competitors_canonical_set

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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds meaningful behavioral context beyond that: results are aggregated by registered domain, ranked by cross-engine consensus, and include per-engine breakdown plus top URLs. It does not mention latency or cost of fanning out across up to seven engines.

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 tight sentences, front-loaded with the core action and its output shape, then the intended use case. No redundant restatement of the name or title and no 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?

An output schema exists, so return-value explanation is not required, and the description still summarizes the return shape (consensus ranking, per-engine breakdown, top URLs). Parameter docs are fully covered by the schema. The only gap is practical guidance around multi-engine fan-out cost or latency for a tool with a 7-engine open-world dependency.

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 five parameters (query, top_n, engines, max_results, exclude_domains) are already documented in the schema itself. The description reinforces the domain-level grouping concept but adds no syntax or default detail beyond the schema, 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?

The description opens with a specific verb+resource: 'Fan a query across engines and aggregate citations by registered domain (not URL).' The parenthetical explicitly disambiguates the aggregation granularity, and the response shape (ranked domains with per-engine breakdown) is stated so an agent can distinguish this from siblings like competitors_compare and competitors_compete.

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?

'Use to identify the canonical competitor set for a query - the domains every engine treats as authoritative' gives clear context for when to reach for this tool. However, it never names or excludes the closely related competitors_compare/competitors_compete siblings, leaving the agent to infer the boundary between them.

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