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

Goes well beyond the annotations: it discloses the return shape (ranked matches with relevance score, endpoint, and carrying registries), warns that the score is not a trust or safety rating, explains the provenance of price terms (publisher manifest or the endpoint's own 402 answer) and that the caller pays the provider directly, and states the rate/price model. That is exactly the context readOnlyHint/openWorldHint/idempotentHint cannot convey.

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 search action and scope, then return shape, then the score caveat, then payment mechanics — a sensible priority order with no filler. It is dense to the point of being a long paragraph, and the payment sentence packs several distinct facts that an agent must unpack.

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 fully covers return values (ranked matches, score, endpoint, registries), the meaning of the score, and the cost model including the free tier — the things an agent needs before committing to a call. Federation behavior is only lightly covered ("at once" here, the faster-off note lives in the schema), but nothing blocking 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 coverage is 86%, so the schema already carries most parameter meaning; the description still adds value by explaining the payment filter categories and that price terms come from manifests or 402 answers, with direct provider payment. It does not touch limit, network, or federate, which are left entirely to the schema.

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 a well-enumerated resource set ("MCP server, skill, agent, API or other callable capability") plus scope ("across this index and every other public ARD registry at once"), which is concrete enough to act on. It never names its closest sibling find_tool, so an agent cannot tell from the description alone which of the two to pick.

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?

Usage is implied by "for a task" and by the filter guidance on payment ("free, payable, x402, mpp"), but there is no explicit when-to-use/when-not and no named alternative such as find_tool or registry_stats. The cost note ("2 free calls a day, then 0.1 USDC") does give the agent a practical budget consideration without saying what to do about it.

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