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

The readOnlyHint annotation already establishes this is a non-mutating read, and the description adds genuine value by disclosing what the comparison returns (auth, free tier, HTTPS, pricing, docs summary) and the 2-5 input bound. It does not describe output format or any rate/size limits, but for a read-only compare that is a minor gap.

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, zero filler. The operation and its scope are front-loaded, with the prerequisite tucked into a short second sentence.

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 single-parameter, read-only tool with no output schema, the description covers the compared attributes and input source, which is most of what an agent needs. It omits any note on how results are returned or ordered, a minor shortfall given the absent output schema.

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 0%, so the description must carry meaning, and it does by stating the slugs come from search_apis and that 2-5 are needed. The count constraint partly restates the schema's minItems/maxItems, and the slug string format itself is never specified.

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) and resource (APIs) plus the exact comparison dimensions (auth, free tier, HTTPS, pricing, docs summary) and the decision it supports ('to choose one'). It is clearly distinguishable from read-oriented siblings like get_api and search_apis.

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?

Explicitly names search_apis as the source of the required slugs, which tells the agent the prerequisite step before calling. It does not state when-not to use it versus get_api or get_deal, so it stops short of full alternative routing.

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