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

The description adds substantial context beyond the annotations: the lookup is free, it never charges or creates another payment, and it returns the existing receipt ID only when one is present. One tension remains: it calls the operation "read-only" while the annotations declare readOnlyHint=false, so an agent cannot tell whether the lookup itself writes a receipt record; this is a minor inconsistency rather than a substantive misdirection, because destructiveHint=false and idempotentHint=true agree with the description that the operation is safe.

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, front-loaded, with the precondition first, the parameter rule second, and the behavioral guarantees last. Nothing is wasted; the capitalized ONLY/EXACT/NEVER is emphatic but each word carries a distinct constraint.

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?

For a single-parameter tool with no output schema, the description covers the happy path and the no-charge guarantee well. It is silent on what happens when no receipt exists, specifically whether the response is indistinguishable from a miss; for a privacy-preserving ledger lookup, that gap matters.

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%, so the schema itself already supplies the baseline documentation of the single parameter. The description still adds real value by saying the digest must be computed locally from the EXACT original Payment-Signature value and never the raw signature; this is operational guidance the schema does not give.

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 (recover an already-reserved owned-API receipt) and frames the exact situation it serves: the buyer paid and lost the HTTP response. It does not, however, say how it differs from the confusingly similar sibling kevaremesh_recover_owned_result, which an agent could easily confuse this with.

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?

"Use ONLY if the buyer already submitted a signed x402 payment but lost the HTTP receipt response" is a strong, explicit precondition that scopes usage, and the warning to send the hash rather than the raw signature is a useful guardrail. It stops short of a score of 5 because it does not name an alternative such as recover_owned_result or find_owned_api, so the agent must infer which tool to use when the receipt response was not lost.

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