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

No annotations are provided, so the description carries the full burden. It usefully discloses the return contents (endpoints, prices, probed trust scores) and the implied read-only nature of a search, but says nothing about cost, auth, rate limits, or result limits/pagination for a live registry query.

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: the first states the action and the search criterion, the second states the return payload. Nothing is padded and the purpose is front-loaded.

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 correctly summarizes the returned fields (endpoints, prices, trust scores), covering the main gap. Minor omissions remain around result volume, pagination, and failure behavior, but nothing essential to invoking the tool 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 100% for the single 'need' parameter, so the baseline is 3. The description goes beyond the schema by supplying two concrete example queries, which clarifies that the parameter is a free-text capability description rather than a structured identifier and helps the agent phrase the value.

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 gives a specific verb and resource ('Search the AgentIndex registry for x402 services') and names the matching criterion ('matching a capability'), so the tool's function is unambiguous. It stops short of differentiating itself from siblings such as check_trust or resolve_data_need, which an agent must infer from names alone.

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?

Concrete query examples ('weather data', 'token prices') imply when the tool is appropriate, and the registry-search framing makes the context reasonably clear. However, there is no statement of when NOT to use it or which sibling (resolve_data_need, get_verified_data) should be preferred under what conditions.

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