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

With no annotations, the description carries the full burden and does substantial work: it states the operation is free, names the catalogs searched, discloses the result cap ('up to 10 matches'), enumerates the kind values, and explains the matched:false signal. It omits rate limits, pagination/ordering behavior, and latency characteristics, but the essential behavioral profile of a read-only discovery call is conveyed.

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?

The most important qualifier ('Free') is front-loaded, then sources, then input guidance, then return shape and the failure signal — a sensible information order with no filler sentences. The standalone 'Free.' fragment is immediately restated by 'Free search across…', a small redundancy that keeps it short of a 5.

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?

No output schema exists, and the description compensates by enumerating the returned fields (kind, URL, price, networks, howToUse) and the matched flag. For a 4-parameter read-only search with no annotations, the only meaningful gap is the missing handoff to report_unmet_need when matched is false.

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 baseline is 3; the description adds the practical point that results are capped at 10 and that each match carries price, payment networks and howToUse, which clarifies what the returned records mean. It does not add format or syntax guidance for need/limit/maxPriceUsd beyond the schema's own descriptions, so it stays near but above baseline.

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?

'Free search across public agent-tool catalogs — paid x402 APIs and MCP tools (PayAI's x402 Bazaar) and MCP servers (the official MCP Registry)' names a specific verb, the exact resource, and the concrete upstream sources. Nothing about the function is left ambiguous, and it is clearly a discovery tool rather than the sibling's reporting function.

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?

The description implies when to use it ('Describe what you need in plain words') and flags the negative outcome ('matched: false means nothing covered your request well'), which suggests the usage boundary. However, it never names report_unmet_need as the follow-up when matched is false, so the actual routing decision between the two siblings is left to inference.

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