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

Annotations already declare readOnlyHint, destructiveHint, idempotentHint, and openWorldHint, so the safety profile is covered. The description adds useful non-schema context (free during validation, no key/credits/wallet, limits apply), but never clarifies what 'selected direct' changes are detected or the nature of the diff output, leaving real behavioral gaps.

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?

Three short sentences, front-loaded with the core capability before the pricing/limits caveats. No waste, though the 'FREE' framing is more promotional than informative.

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?

An output schema exists so return values needn't be explained, and the read-only nature is covered by annotations. However, the scope of 'selected direct breaking changes' and what limits 'apply' remain undefined, which is a meaningful gap for a diff 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 coverage is 67% and the description says nothing about the parameters, relying on the schema's before/after nested objects and the legacy requestId/maxPriceMicroUsd fields. It only implicitly confirms the inputs are OpenAPI documents, so it adds little beyond the schema; baseline 3.

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?

States a specific verb+resource: detecting breaking changes between OpenAPI 3.0 documents, which cleanly separates it from siblings like contracts_openapi_lint and contracts_jsonschema_validate. The qualifier 'selected direct breaking changes' is slightly ambiguous about which changes are covered, keeping it from a 5.

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 indication of when to choose this over contracts_openapi_lint or contracts_jsonschema_validate, and no prerequisites beyond the vague 'existing source and input limits apply'. The pricing note is not usage guidance.

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