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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds genuine behavioral value by disclosing the result taxonomy and the five granularity levels at which changes are classified, which is important given there is no output schema. It stops short of describing edge cases (unresolvable refs, ambiguous version inputs).

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?

A single dense sentence with the action front-loaded and the scope qualifier trailing. Every clause earns its place; nothing is repeated from the title or annotations.

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 three-parameter, fully documented, read-only tool with no output schema, the description covers what the tool returns (change classification at multiple granularities). It does not mention input format flexibility (string path/URL vs. object) or result size/ordering, leaving a small gap.

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%, including the baseline/candidate semantics and aliases, so the schema carries the parameter burden. The description adds no parameter-level detail (e.g., accepted string forms vs. inline objects) beyond what the schema already states, so the baseline 3 applies.

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 (compare/diff) and resource (two OpenAPI versions) plus the exact output taxonomy (breaking, non-breaking, addition) and the granularity levels (path, operation, parameter, request-body, response). No sibling in the list (api_scorecard, validate_api, api_coverage) performs a version diff, so the tool is clearly distinguishable.

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?

Usage is implied by the name and description — you call it when you have a baseline and a candidate spec to compare — but the description never states prerequisites, when to prefer it over validate_api/api_scorecard, or any exclusions. Minimum viable routing guidance.

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