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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered. The description adds genuinely useful behavioral context beyond that: result-payload shape (compact summaries, price in decimal USD, uptime, status, verification) and the one-page-of-up-to-100 boundary. It stops short of rate limits or server-side filtering cost caveats that the schema's 'per_page' note hints at.

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?

Three sentences, front-loaded with the routing instruction that matters most. The middle sentence is dense with filter/sort enumeration that largely duplicates the schema, costing a little against pure conciseness.

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 10 params, no output schema, and a directory-scale read, the description covers the essentials: trigger, filter/sort axes, response granularity and size, and the escalation path to the detail tool. Minor gaps are pagination mechanics and how it relates to the sibling ranking/assessment tools.

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% and every parameter carries its own detailed description, including the nuanced signable semantics. The description only restates the filter dimensions (query, category, network, status, signable) and sort orders in prose, adding no syntax or format information beyond the schema, so 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 and resource ('narrows the directory of listed services to candidates') and frames itself as the discovery entry point. It explicitly distinguishes itself from the sibling x402_get_service, whose job is the full record, so an agent can route without opening a schema.

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 opening clause gives a clear trigger condition ('Your first call when you do not know which x402 service exists for a job') and names the follow-up alternative x402_get_service. It does not address when to prefer x402_find_best_service or x402_assess_services instead, so the guidance is strong but not exhaustive.

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