validate_dmarc_record

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

Annotations already indicate readOnlyHint and idempotentHint, and the description adds meaningful behavioral context: it performs no DNS lookup, accepts only a pasted record string, reports parsed tags and findings, and explains the alignment-evidence limitation. The upgrade_record policy explanation also clarifies an important boundary. No contradiction with annotations.

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 and remaining sentences add useful routing and policy context. The upgrade_record/p=reject explanation is somewhat lengthy for a validation tool, but it earns its place by preventing misuse.

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?

With a single parameter, no output schema, and annotations covering safety, the description provides enough detail: what it validates, what it returns at a high level, what it does not do, and how it relates to upgrade paths. The agent can call it correctly without additional context.

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 already provides strong coverage (100%) with an example and the 'record value only' clarification. The description reinforces this by saying 'pass the record string itself' and explicitly excluding DNS lookup, adding slight value beyond the 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 opens with a specific verb and resource: 'Validate a pasted DMARC record', then lists concrete outputs (parsed tags, level'd findings, validity). It clearly distinguishes itself from DNS-lookup and record-generation siblings by explicitly stating 'No DNS lookup' and by contrasting with upgrade_record.

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?

It explicitly states when to use the tool ('pass the record string itself') and when not to use a scan-based alternative, explaining why upgrade_record is capped at p=quarantine and that p=reject requires aggregate-report evidence. This gives the agent actionable selection criteria.

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