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

Goes well beyond the annotations by disclosing the authentication model (Ed25519 signature verified server-side), the default state ('Receipts are private by default'), and the fact that no x402 payment is layered on. It does not spell out the consequence of flipping opt_in to false in terms of what becomes hidden from other readers, so it's not exhaustive against destructiveHint=true.

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 action and signature recipe, which is good, but the free/no-payment point is made three times ('FREE — no payment required', 'no x402 challenge; this tool is free', 'the MCP layer adds no payment'). That redundancy displaces room for the unresolved `id` parameter.

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 signed mutation with no output schema, the description covers auth, cost, and defaults but leaves gaps: the response shape, failure modes for an invalid signature, and the id/operator_id relationship are all unstated. Adequate to start, not complete for a destructive-flagged write.

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 only 25%, but the description compensates heavily for `signature` by giving the exact canonical string and the literal true/false encoding for opt_in. However, it never explains what `id` is, and the presence of both `id` and `operator_id` (which appear in the same canonical string) is left ambiguous.

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+resource ('Toggle your own receipts visibility') and parenthetically classifies it as an operator-key-signed write, which immediately distinguishes it from the read-side sibling commons_get_receipts. It never names a sibling or explicitly excludes one, so it stops short of a 5.

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?

The description conveys the operational context (must be signed, free, no payment challenge, defaults to private) but never says when to use this versus alternatives or when not to use it. The user must infer that this only affects the caller's own operator record.

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