nslookup.io MCP Server

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries the full burden of behavioral disclosure. It describes what the tool returns (BIMI DNS record status, VMC certificate details, etc.), which is helpful, but doesn't mention error handling, rate limits, authentication requirements, or whether it's a read-only operation. The description adds value but lacks comprehensive behavioral context.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, well-structured sentence that efficiently conveys the tool's purpose and return values. It's front-loaded with the main action and provides specific details without unnecessary elaboration, making every word count.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's moderate complexity (checking multiple verification aspects), no annotations, and no output schema, the description is adequate but incomplete. It specifies what information is returned but doesn't cover error cases, format of return values, or operational constraints. It meets minimum viability but leaves gaps in contextual understanding.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the schema already documents the single parameter 'domain' with an example. The description adds no additional parameter semantics beyond what's in the schema. With only one parameter, the baseline is 4, as minimal parameter explanation is needed.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the specific action ('Check BIMI and VMC for a domain') and the resources involved (BIMI DNS record, VMC certificate, logo URL, trademark info, expiry). It distinguishes itself from sibling tools like dns_lookup or ssl_certificate by focusing specifically on BIMI/VMC verification rather than general DNS or SSL checks.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage context (checking BIMI/VMC for domains) but doesn't explicitly state when to use this tool versus alternatives like dns_record or ssl_certificate. No guidance is provided about prerequisites, exclusions, or specific scenarios where this tool is preferred over siblings.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries the full burden. It discloses the tool's behavior by specifying the types of DNS records returned and the server querying aspect. However, it lacks details on rate limits, error handling, or response format, which are important for a network tool. The description does not contradict any annotations, as none exist.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is two sentences that are front-loaded with the core purpose and efficiently detail the parameters and server behavior. Every word contributes to understanding the tool's functionality without redundancy or unnecessary elaboration.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given no annotations and no output schema, the description adequately covers the tool's purpose and parameters. However, as a network query tool, it lacks details on output structure, potential errors, or performance considerations, which would be helpful for an agent. It meets minimum viability but has gaps in completeness.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the baseline is 3. The description adds value by clarifying the scope of DNS records (listing A, AAAA, etc.) and explaining the 'server' parameter's default and the 'authoritative' option, which enhances understanding beyond the schema's enum list. This elevates the score to 4.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the action ('look up'), the resource ('DNS records'), and specifies the scope ('all common DNS records: A, AAAA, NS, MX, TXT, CNAME, SOA'). It distinguishes itself from siblings like dns_propagation or dns_record by emphasizing comprehensive record retrieval rather than specific checks or single-record operations.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage for DNS queries with server options, but it does not explicitly state when to use this tool versus alternatives like dns_record or dns_propagation. It mentions a default server and the 'authoritative' option, which provides some context, but lacks clear guidance on tool selection among siblings.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries the full burden. It discloses the tool's behavior by specifying the number and types of DNS servers checked and the purpose (checking propagation status). However, it lacks details on rate limits, authentication needs, error handling, or response format, which are important for a tool that queries external servers.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is front-loaded with the core purpose in the first sentence and adds clarifying details in the second. Every sentence earns its place by specifying the scope and outcome without redundancy or unnecessary elaboration.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's moderate complexity (querying multiple external servers) and lack of annotations and output schema, the description is somewhat complete but has gaps. It covers the purpose and scope well but omits behavioral details like response structure, potential delays, or error conditions that would help an agent use it effectively.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the schema already documents both parameters thoroughly. The description doesn't add any additional meaning beyond what's in the schema (e.g., it doesn't explain parameter interactions or provide usage examples). Baseline 3 is appropriate as the schema does the heavy lifting.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the specific action ('Check DNS propagation') and resource ('for a domain'), including the scope ('across 18+ global DNS servers') and examples of servers. It distinguishes from sibling tools like 'dns_lookup' by focusing on propagation status rather than general DNS querying.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage context ('Shows if DNS changes have propagated worldwide'), which suggests it's for verifying recent DNS updates. However, it doesn't explicitly state when to use this versus alternatives like 'dns_lookup' or 'dns_record', nor does it mention exclusions or prerequisites.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries the full burden of behavioral disclosure. It states the tool performs a lookup but doesn't describe what the lookup entails—whether it's a read-only query, if it requires authentication, potential rate limits, error conditions, or what the response format might be. For a tool with 3 parameters and no output schema, this is a significant gap in transparency.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is concise and front-loaded, with the core purpose stated clearly in the first sentence. The second sentence adds useful context about supported record types without unnecessary elaboration. However, it could be slightly more structured by explicitly separating functionality from examples.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's complexity (3 parameters, no output schema, no annotations), the description is incomplete. It doesn't explain what the tool returns, how results are formatted, error handling, or performance considerations. For a DNS lookup tool with multiple configuration options, more context is needed to guide effective use.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The description adds minimal value beyond the input schema, which has 100% coverage. It lists example record types ('including A, AAAA, MX, TXT, CNAME, SOA, PTR, CAA, SRV, DNSKEY, DS, TLSA, HTTPS, SPF, and more') but doesn't explain their purposes or when to use specific types. The schema already documents parameters thoroughly, so the baseline score of 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's purpose: 'Look up a specific DNS record type for a domain.' It specifies the verb ('look up'), resource ('DNS record'), and scope ('specific type for a domain'), making it easy to understand. However, it doesn't explicitly differentiate from sibling tools like 'dns_lookup' or 'dns_propagation', which prevents a perfect score.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides no guidance on when to use this tool versus alternatives. It mentions 'Supports 53 record types' but doesn't explain when to choose this over sibling tools like 'dns_lookup' or 'dns_propagation'. There's no mention of prerequisites, exclusions, or typical use cases, leaving the agent to infer usage context.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries full burden. It discloses the tool's purpose and output format (findings with severity levels), but doesn't mention behavioral aspects like execution time, rate limits, authentication requirements, or whether it performs active probing versus passive analysis.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is perfectly concise with two sentences: the first states the action and scope, the second describes the return format. Every word contributes essential information with zero waste.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a single-parameter tool with no annotations and no output schema, the description provides good coverage of purpose and output format. However, it could better address behavioral aspects like execution characteristics or error conditions given the tool's security scanning complexity.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100% with the single 'domain' parameter fully documented. The description doesn't add any parameter-specific information beyond what the schema provides, maintaining the baseline score for high schema coverage.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the specific action ('Run a security scan') and resource ('on a domain'), listing concrete vulnerability types (DNS misconfigurations, SPF/DKIM/DMARC records, cookie security issues) and distinguishing it from sibling tools like dns_lookup or ssl_certificate that perform narrower checks.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage for comprehensive security vulnerability detection on domains, but doesn't explicitly state when to use this tool versus alternatives like dns_lookup (for specific DNS queries) or ssl_certificate (for SSL/TLS checks). No explicit exclusions or prerequisites are provided.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries the full burden. It discloses the return data (issuer, expiry date, etc.) and implies a read-only operation, but lacks details on error handling, rate limits, authentication needs, or network dependencies. It adds value by specifying output content but misses key behavioral traits.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is front-loaded with the core purpose in the first sentence, followed by a concise list of return values. Every sentence earns its place, with no wasted words, making it efficient and easy to parse.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's moderate complexity (single parameter, no output schema, no annotations), the description is adequate but incomplete. It covers the purpose and output semantics well, but lacks usage guidelines and behavioral details like error cases or performance expectations, leaving gaps for an agent.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the schema already documents the single 'domain' parameter. The description adds no additional parameter details beyond what the schema provides, such as format examples or constraints, meeting the baseline for high schema coverage.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the specific action ('Check the SSL/TLS certificate for a domain') and the resource ('domain'), distinguishing it from sibling tools like dns_lookup, security_scan, or uptime_check by focusing exclusively on SSL/TLS certificate inspection.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

No guidance is provided on when to use this tool versus alternatives. While the purpose is clear, there's no mention of prerequisites, limitations, or comparisons to sibling tools like security_scan, which might overlap in functionality.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries the full burden of behavioral disclosure. It describes the tool as a 'one-time' check (not continuous monitoring) and specifies the return data (status, code, response time), but does not mention error handling, rate limits, authentication needs, or network constraints. This covers core functionality but leaves gaps in operational details.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, efficient sentence that front-loads the purpose and key return values without unnecessary words. Every element ('one-time HTTP uptime check', 'URL', 'returns...') serves a clear purpose, making it easy to parse and understand quickly.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's moderate complexity (HTTP check with timing), no annotations, and no output schema, the description provides a solid foundation but lacks details on error responses, retry behavior, or output structure. It is complete enough for basic use but would benefit from more context on failure modes or performance characteristics.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, with both parameters ('url' and 'timeout') well-documented in the schema. The description does not add any parameter-specific details beyond what the schema provides, such as URL format examples or timeout implications. Baseline score of 3 is appropriate as the schema handles parameter documentation adequately.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the specific action ('perform a one-time HTTP uptime check'), the resource ('on a URL'), and the outcome ('returns whether the site is up or down, HTTP status code, and response time'). It distinguishes itself from sibling tools like 'security_scan' or 'ssl_certificate' by focusing solely on uptime monitoring rather than security or certificate analysis.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage for checking website availability with timing metrics, but does not explicitly state when to use this tool versus alternatives like 'security_scan' for vulnerability checks or 'dns_lookup' for DNS issues. It provides basic context but lacks explicit guidance on exclusions or prerequisites.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries full burden but only states what the tool returns, not behavioral traits like rate limits, error handling, or network dependencies. It lacks details on performance, caching, or potential failures.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, well-structured sentence that efficiently conveys the tool's functionality without unnecessary words. It is front-loaded with the core purpose and includes all relevant details concisely.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple lookup tool with one parameter and no output schema, the description covers the basic purpose and return types adequately. However, it lacks behavioral context and sibling differentiation, leaving gaps in completeness.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the schema fully documents the 'domain' parameter. The description adds no additional parameter semantics beyond what the schema provides, meeting the baseline for high coverage.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's purpose with specific verbs ('Get', 'look up') and resources ('IP addresses', 'A and AAAA records', 'punycode and unicode domain representations'). It distinguishes from siblings by focusing on IP address retrieval rather than broader DNS lookups or security checks.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

No explicit guidance on when to use this tool versus alternatives like 'dns_lookup' or 'dns_record' is provided. The description implies usage for IP address lookups but doesn't specify scenarios where this tool is preferred over siblings.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.