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

No annotations are provided, so the description must cover behavioral traits. It states 'finalizes the purchase' (a write operation) and lists returns, but does not disclose idempotency, failure behavior, side effects, or required permissions.

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 has a clear Args/Returns structure, but it redundantly lists all parameter descriptions which are already explained. Slightly verbose but still well-organized.

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 an output schema exists (context signals confirm), the description adequately covers inputs and returns. However, it lacks details on error handling, idempotency, and edge cases.

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 schema has 0% description coverage, but the description fully explains each parameter's purpose (e.g., 'merchant_url: The base URL of the UCP-enabled merchant'). This adds substantial meaning beyond the raw schema.

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 completes a checkout session by submitting payment and finalizing the purchase. It uses a specific verb ('complete') with a clear resource ('checkout session'), and is distinct from sibling tools like create, update, or discover.

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 this is the final step in the checkout process but does not explicitly state when to use it versus alternatives (e.g., update or create). No guidance on prerequisites or when not to use.

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?

No annotations are provided, so the description must disclose behavioral traits. While it explains inputs and outputs, it omits details like side effects (does this create a persistent session?), required authentication, idempotency, or error conditions. The fact that it 'creates' implies mutation, but no further safety or state info.

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 well-structured with 'Args' and 'Returns' sections, each parameter on a separate line. It is concise enough—5 parameters described in a few sentences—but could be slightly more compact by omitting the explicit 'Args' label if not needed.

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 5 parameters, no annotations, and presence of an output schema, the description covers all inputs and defines the return structure. However, it lacks mention of authentication, error handling, or prerequisites (e.g., merchant must be discoverable via ucp_discover). Enough for basic use but not exhaustive.

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 has 0% description coverage, but the description fully compensates by explaining each parameter's meaning, including the structure of 'items' (list with 'id' and 'quantity') and default for 'currency'. All 5 parameters are clearly defined, and the return dictionary is detailed.

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 ('Create a new checkout session') and the resource ('UCP merchant'). It provides specific parameter explanations and return values, but does not explicitly differentiate from sibling tools like ucp_checkout_complete or ucp_checkout_update.

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 on when to use this tool versus alternatives. The description does not mention prerequisites, typical workflow (e.g., start a checkout before completing it), or scenarios where another sibling would be appropriate. Sibling tool names are listed but without 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?

No annotations are provided, so the description carries full burden. It discloses the key behavioral trait: 'Automatically selects the first available shipping address and delivery option,' informing the agent of this autonomous action.

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, front-loading the purpose and usage guidance. It includes structured Args and Returns sections, making it easy to scan. A slight reduction in verbosity could be possible, but overall it's efficient.

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 simple 2-parameter schema and presence of an output schema, the description adequately covers purpose, when to call, behavioral details, and return fields. It could mention error conditions but is sufficiently complete for this tool.

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 0%, but the description only lists the parameter names without adding meaning. The parameter names (merchant_url, checkout_id) are self-explanatory, but the description fails to provide additional context or constraints.

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: 'Set up shipping/fulfillment for a checkout.' It also explains automatic selection of shipping address and delivery option, distinguishing it from sibling tools like ucp_checkout_complete or ucp_checkout_create.

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 includes explicit usage guidance: 'Must be called before completing checkout if the merchant requires fulfillment.' This tells when to use it, though it does not mention when not to use or alternatives.

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?

No annotations are provided, so the description must fully disclose behavior. It mentions updating and applying discount codes but fails to clarify whether the tool only updates discount codes (as suggested by parameters) or other fields, nor does it address side effects, idempotency, or authorization.

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 with a clear summary, args section, and returns section. Every sentence serves a purpose, and the structure is 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?

The description includes a detailed return structure in the missing output schema. However, it omits error conditions, prerequisites, or limitations. Given the output coverage, it is fairly complete.

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?

With 0% schema description coverage, the description adds meaning to all three parameters: merchant_url (base URL), checkout_id (ID), and discount_codes (list of codes). This compensates for the schema's lack of descriptions.

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 updates an existing checkout session, with an example of applying discount codes. It differentiates from sibling tools like create, complete, and set_fulfillment, which handle distinct stages.

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 modifying a session (e.g., applying discount codes) but does not explicitly contrast with siblings or provide when-not-to-use guidance. No exclusions or alternatives are mentioned.

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 the full burden. It explains the input and output but does not mention side effects, auth requirements, or error conditions. 'Discover' suggests a read-only operation, but this is not explicitly stated.

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 with three distinct sections (summary, args, returns), front-loaded with the purpose, and contains no redundant or irrelevant information.

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?

The description covers the input parameter and return values sufficiently, and an output schema exists. However, it could mention potential failures (e.g., if the merchant is not UCP-enabled) or error handling.

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 meaning to the single parameter 'merchant_url' by explaining it as 'The base URL of the UCP-enabled merchant' and providing an example, compensating for the 0% schema description 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 uses a specific verb 'Discover' and resource 'a merchant's UCP capabilities and supported payment methods', clearly distinguishing it from sibling tools like ucp_checkout_create which focus on checkout 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 this tool is the first step for interacting with a UCP merchant, but it does not explicitly state when to use it versus alternatives or when not to use it.

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