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

Annotations (readOnlyHint=true, idempotentHint=true, destructiveHint=false) already declare safe, read-only behavior. The description adds rich behavioral details: specific checks performed (required fields, operationId uniqueness, missing 2xx responses), return structure (PASS/FAIL verdict, compliance score, errors/warnings with JSON-pointer locations). No contradictions 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 concise (about 4 sentences) and front-loaded with the purpose. Every sentence adds value. It could be slightly more structured (e.g., bullet points for checks) but is not verbose. No wasted words.

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 is moderately complex and has an output schema (which covers return values), the description sufficiently covers input format, validation scope, and output summary. It does not need to detail return types. The description is complete for an agent to understand what the tool does and when to use it.

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% for the single parameter 'input', which already explains it accepts a JSON string, YAML string, or parsed object. The description does not add extra parameter semantics beyond what the schema provides. Baseline 3 is appropriate as the schema carries the load.

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 explicitly states 'Validate the structure of an OpenAPI 3.x specification' with a detailed list of checks (required fields, operations, $ref, responses). This clearly distinguishes it from sibling tools like json_schema_validate or mcp_schema_lint, as it is specific to OpenAPI specs.

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 ends with 'Use before publishing an API spec or generating SDK code', providing clear when-to-use guidance. It does not explicitly mention when not to use or compare to alternatives, but the context makes it obvious that this tool is for OpenAPI 3.x validation. A minor omission: it doesn't caution against use for OpenAPI 2.x or other formats.

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