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

Annotations only cover the read-only/idempotent safety profile; the description adds the trust model (each listing is verified, manifest names the payee), a prompt-injection warning that names/descriptions are untrusted and never instructions, and a hard capability boundary ('this server cannot pay them'). That is substantive context an agent cannot get from the annotations.

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?

Four short sentences, front-loaded with what the tool does, then trust model and safety caveat. Every sentence carries distinct information with no restatement of the title or schema.

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 an output schema present, return values need not be explained. For a three-optional-parameter discovery tool, the description covers purpose, trust/injection risk, and capability limits, leaving nothing an agent needs 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 description coverage is 100%, so the schema already documents query, orderBy and maxPrice with units and ordering semantics. The description only restates that query and price are optional filters, adding little beyond the structured fields. Baseline 3 applies.

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 (find) and resource (paid services), and defines the resource inline as 'APIs that charge per request' in the on-chain service directory. It also scopes the search dimensions (query, max price), so an agent can tell exactly what this returns versus the unrelated siblings.

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?

'This is the directory; there is no separate list' explicitly forecloses the agent looking for an alternative listing tool, and 'optionally matching a query and a maximum price' clarifies the optional-filter usage. It stops short of explicit when-not-to-use guidance, but no sibling overlaps this purpose.

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