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

Annotations declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=true, covering safety and idempotency. The description adds valuable context: 'Pass required,' 'one signed answer,' and the fact that it reuses a result up to 5 minutes old unless force is true. It reveals that the result is signed and includes a recommendation, which goes beyond annotations. It doesn't discuss rate limits or failure modes, but the added detail is substantive.

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?

The description is a single, dense sentence that front-loads the key requirement ('Pass required') and the primary use case. It is appropriately sized for a complex tool and every clause adds information. It could be slightly more scannable, but it avoids waste.

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 explain return values, and it doesn't. It covers the major checks performed, the signed answer, and the cache behavior. However, for a tool with openWorldHint and a claimed 'one signed answer,' it doesn't clarify what the signature guarantees or how the recommendation should be interpreted. Contextual completeness is adequate but not rich.

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 url, pass, and force thoroughly. The description reminds that a pass is required and that force overrides the 5-minute cache, adding meaning beyond the schema for force. It doesn't add syntax or format details for url or pass beyond the schema, so it's slightly better than baseline but not exceptional.

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 states a specific verb and resource: it performs a pre-payment safety check on an unfamiliar x402 endpoint. It enumerates the checks (liveness, quote, payability, payTo existence, seller endpoints, settlement integrity, delivery result, honeypot scan), making the purpose clear. It does not explicitly differentiate itself from siblings like settled_check or settled_verify, but the depth of pre-spend verification distinguishes it contextually.

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 clearly says this is 'the one call to make before paying an unfamiliar x402 endpoint,' which sets the usage context. It implies when to use it (before paying an unknown endpoint) but does not explicitly state when not to use it or name alternative tools for different scenarios. No exclusions or alternatives are given, so it falls short of a 5.

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