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

Adds substantial context beyond the readOnly/non-destructive annotations: it returns one of three status codes, needs no credentials or payment authorization, envelopes are not published or echoed, and it discloses the trust model (fetches OCD's public key registry, trusts this server) plus the limits of VALID. The only wobble is that this 'online check that fetches a registry' sits in mild tension with openWorldHint=false, though the fetch is to the service's own registry.

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?

Front-loads the trigger condition and the return values, then layers the caveats about what VALID does and does not mean. It is long but nearly every clause carries decision-relevant information; a couple of sentences could be tightened.

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 no output schema, the description carries the burden of explaining returns and does so fully (VALID/INVALID/UNVERIFIABLE with the precise meaning of VALID and its non-guarantees), plus the no-credentials envelope privacy rule. An agent has everything needed to call and interpret it.

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 50% (receipt_id is undocumented in the schema), and the description compensates by framing the two inputs as mutually alternative ('one public receipt_id OR an envelope'), stressing the receipt_id must be public, and defining what it is safe to put in an envelope (no credentials, no payment authorizations). It adds real meaning over the schema.

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 (verify) and resource (an OCD receipt proof), and immediately clarifies the question it answers: whether a receipt is authentic or its evidence signature checks out. This is clearly distinguishable from siblings like get_receipt or inspect_payment, which retrieve rather than validate.

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?

Gives a clear trigger condition ('Use this when the user wants to know whether an OCD receipt proof is valid') and names an alternative approach (offline verification is stronger). It does not explicitly contrast with the sibling retrieval tools, so it stops short of full when/when-not routing.

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