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

Annotations already declare readOnlyHint and openWorldHint; the description adds real value beyond them by disclosing cost ('Free to call') and side-effect boundaries ('never pays and never signs anything'). It doesn't mention rate limits or what happens if the well-known route is unavailable, so a small gap remains.

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?

Three short sentences, front-loaded with what it reads and what it returns, followed by cost and safety guarantees. Every sentence carries distinct, useful information with no repetition of the title.

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 must convey the return: it does ('paid endpoints with their prices in USDC'). It omits the response shape (e.g., mapping of route to price) and pagination/error behavior, but for a simple manifest read this is close to sufficient.

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 tool takes zero parameters, so there is nothing for the description to disambiguate; the description correctly signals a no-argument call. Baseline 4 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?

States a specific verb and resource ('Reads GET /.well-known/x402 ... returns the paid endpoints with their prices in USDC') and names the upstream sources. It does not, however, differentiate itself from the similarly named sibling receipts_index, leaving some ambiguity about which index tool to pick.

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?

Clearly frames this as a discovery/pricing lookup ('Free to call') and explicitly redirects the actual payment step elsewhere ('Paying is done by an x402 client against the listed route'). No explicit when-not or comparison to receipts_index/receipts_sample, but the intended context is unambiguous.

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