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

Annotations already cover safety (readOnlyHint, destructiveHint=false) and openness, so the description's main value-add is the disclosed cost: "Counts as one of the 5 free daily audits" — a quota constraint an agent cannot infer from any structured field. The 30-day retention note appears in the schema rather than the description, and nothing is said about failure modes for expired IDs. No contradiction with readOnlyHint, since auditing does not mutate the target site.

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?

Two sentences, front-loaded with the action, then the result categories, then the usage trigger, then the quota caveat. Every clause conveys distinct operational information with no restatement of the name or title.

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 only two required, fully documented parameters, annotations declaring safety, and no output schema, the description carries precisely what is missing: what the comparison returns, when to reach for it, and that it consumes daily quota. Nothing an agent needs in order to call it correctly is absent.

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% and both parameters carry their own examples and patterns, so the schema does the heavy lifting. The description only reinforces the "same site" constraint on url; it adds no format or edge-case guidance for previous_audit_id beyond what the schema states.

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?

Specific verb and resource: "Run a fresh audit of the same site and compare it with an earlier audit," followed by the exact output taxonomy (fixed, improved, still failing, worse, new) plus before/after score. That output description cleanly separates it from audit_site without needing the schema.

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?

Explicit trigger: "Use after making changes suggested by audit_site," which also implies audit_site is the tool for a first-time audit. It adds a real precondition in the schema-adjacent constraint of the page being "on the same site as the earlier audit," but never states a when-not case (e.g. what to do if no prior audit exists).

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