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

No annotations, so the description carries the full burden and does so well: it explains exampleEvidence provenance tiers (paid-run/challenge/docs), sanitisation and validation of merchant schemas, endpointCheck semantics, the fee exclusion, and unknown-slug error behavior. Minor gap: it could state whether there are rate limits or auth requirements.

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 action and workflow, but the middle is a dense run-on of provenance jargon (paid-run/challenge/docs, sanitisation rules, endpointCheck) that is hard to parse and could be tightened.

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 1-param discovery tool with no output schema, the description covers return shape (metadata, requestShape, invoke contract, schemas, examples), edge cases (unknown slug), and next steps. It is slightly overloaded with provenance detail an agent rarely needs for selection.

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 the single param is documented there. The description adds meaning beyond the schema by tying the slug to search_services provenance and describing consequences of an unknown slug.

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 ('Fetch one catalog service by slug') and explicitly scopes it as 'Discovery only; no payment.' This distinguishes it from pay_service and quote_service, naming quote_service as the next step.

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 workflow routing: read payServiceArgs before pay_service, call quote_service for the live fee-inclusive total before paying, and the note that discovery carries no payment. When/when-not and the alternative are both named.

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