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

Annotations already cover read-only, idempotent, and non-destructive behavior. The description adds meaningful context about provenance ('canonical x402 rail') and the semantic rule that challenges/signatures are not valid proof, going beyond what the annotations convey.

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 tightly written sentences: the first front-loads the tool's purpose, and the second adds a distinct, important caution. There is no filler, repetition, or unnecessary detail.

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 no-input, read-only tool, the description is largely complete: it names the resource, the action, and a key interpretative rule. It does not describe the structure of the returned evidence, but with no output schema and no parameters, that is a minor gap rather than a critical omission.

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?

The input schema has zero parameters and is fully covered, so there is no parameter ambiguity for the description to resolve. The baseline for a no-parameter tool applies, and the description appropriately does not invent unnecessary parameter details.

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: 'Read real settlement evidence recorded by the canonical x402 rail.' The caveat about challenge or signature not being proof further clarifies that this tool is the authoritative evidence source, distinguishing it from related x402 tools.

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 clearly indicates that this tool is for retrieving real settlement evidence. The warning that a challenge or signature alone is never treated as revenue/settlement proof provides implicit when-not-to-use guidance, though it does not explicitly name sibling alternatives.

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