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

Annotations cover the safety profile (readOnly/idempotent/openWorld), and the description adds substantial context beyond them: pay-per-call key budget consumption, required env-var credential, exact failure reasons ('not_configured', 'no_domain'), one API call per check, no pagination, and query-only with no submission API.

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 core purpose, and each sentence carries real information (pricing model, credential, error states, pagination limits). It is dense and the em-dash asides make it longer than strictly necessary, but nothing is filler.

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 output schema, the description compensates fully by describing the response contract: the engine marker on every success and the two failure reasons. For a paid, credentialed, single-call tool, nothing an agent needs to call it correctly is missing.

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%, so all seven parameters are already documented. The description reinforces semantics (targetDomain defaulting to the project domain, depth being Brave's ceiling, competitorDomains being free within the fetched set) but adds little that the schema does not already state; 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 and resource ('Checks where a project's domain ... ranks in REAL Brave Search results for one keyword') and immediately distinguishes itself from the server's free SearXNG/openserp-backed rank checks by naming the engine. An agent can tell it apart from other rank tools without opening 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?

Gives strong context: it is a PAID, bring-your-own-key tool requiring BRAVE_SEARCH_API_KEY, and it contrasts itself with the free-tier rank checks. However, it never names a specific sibling tool to use instead when the paid source is not wanted, so routing is inferred from category rather than an explicit alternative.

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