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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered; the description adds the non-obvious behavioral fact that the returned artifact is time-dependent (proof appears only after epoch close), which explains the unusual idempotentHint=false on a read. It does not address error behavior for unclosed epochs or unknown task ids, so not a 5.

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?

A single front-loaded sentence with the action and resource first and the field list trailing as a parenthetical. Slightly dense, and the enumerated return fields partially duplicate the output schema, but nothing is wasted.

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 an output schema present, the description needn't explain return values, yet it does briefly; the critical missing piece would be what happens when the epoch is still open, which is only implied. Overall it gives an agent enough to invoke correctly.

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 the single parameter is documented in the schema with its origin ('task id from chat / embed (0x…)'). The description only restates 'by task id' and adds no format, sourcing, or failure semantics beyond the schema, so the 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?

Specific verb ('Fetch') plus specific resource ('public receipt of a paid request'), keyed by task id, and it enumerates the payload contents (model, provider, tokens, price, settlement tx, hashes, signatures, Merkle proof). This is clearly distinguishable from every sibling (chat, embed, usage, quote, route_explain), none of which read settlement artifacts.

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?

States the applicability conditions explicitly: it only applies to a *paid* request, and the Merkle proof portion only materializes 'once the weekly epoch is closed'. That is real usage context an agent needs. It stops short of stating exclusions or naming an alternative when the epoch is not yet closed, 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.