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

No annotations are supplied, so the description carries the full behavioral burden. It does well on cost/limit (free, 100/day per wallet, caller-keyed) and on scope of the response (gradability, census, verdict line, per-class change counts), but it leaves out error/failure modes, what happens when the pair cannot be graded, and what a 'census' or 'verdict line' actually contains. The disclaimer that it is a deterministic mechanical comparison that does not establish code breakage is valuable added context.

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?

Front-loaded with the most decision-relevant facts ('FREE headline breaking-change pre-check'), then formats, then outputs, then the disclaimer. Slightly dense with parenthetical rate-limit and format lists, but every sentence carries information an agent needs.

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 no annotations and no output schema, the description must explain both behavior and returns, and it does list the headline outputs and the cost model. Gaps remain around failure behavior for ungradable pairs and the absence of an explicit handoff to apidiff_diff by name, which keeps it short of 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?

Schema coverage is 100%, so the baseline is 3, but the description adds real meaning beyond the schema: 'pass caller' explains that the caller field keys the free allowance, and 'one submitted document pair' clarifies that the single-pair form is the default while the pairs array is an alternative. It does not repeat the schema's type constraints or explain how version_a/version_b mismatches are handled.

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?

Opens with a specific verb+resource+scope: 'FREE headline breaking-change pre-check of one submitted document pair', and clarifies which document formats are accepted (OpenAPI 3.0.x/3.1.x JSON or JSON Schema pair). It distinguishes itself from the 'paid report' conceptually, but never names the sibling tools (apidiff_diff, apidiff_criteria), so the routing signal is implicit rather than explicit.

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?

Clear situational framing: free headline first, with 'Located findings are in the paid report' telling the agent to escalate elsewhere for detail, plus the 100/day per wallet allowance that governs usage. It lacks an explicit named alternative and doesn't state when this pre-check is unnecessary (e.g., once the paid report is already known needed).

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