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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and openWorldHint=false, so the safety profile is covered. The description adds genuinely new behavioral context: results are returned in published rank order and carry scores, schemes, roles, custody and maturity. It does not mention result caps or pagination behavior, though the limit parameter hints at the former.

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 tight sentences with no filler; the core purpose leads, the result-shape detail follows, and the no-argument behavior is last. Every clause carries information the agent can act on.

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?

An output schema exists, so the description needn't spell out return structure, and rich annotations cover the safety profile. The main gap is filter semantics across the six undocumented parameters, but for a zero-required-argument search tool with self-describing enums this is close to complete.

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 only 13% (only the query parameter is documented), so the description carries real weight here. It says 'Free-text query plus filters' and names schemes and custody/maturity as result facets, which loosely maps to the scheme and self_custodial_only filters, but it never explains kind, role, limit, mcp_native_only, or production_only. The enum values are largely self-describing, which keeps this at a baseline 3.

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 names a specific verb and resource ('Search the 402MCP.org registry of HTTP 402 payment solutions') and scopes it to concrete schemes (L402, x402, MPP), so the agent knows exactly what is being queried. It only implicitly distinguishes itself from siblings like get_solution or get_best_payment_solution by noting that results come back ranked as a list rather than as a single 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?

It gives one concrete usage cue ('Call with no arguments to list the whole registry') and states that free-text query works alongside filters, so basic usage is implied. It never says when to prefer this tool over recommend_payment_rail, get_best_payment_solution, or get_solution, which are the closest alternatives.

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