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

The description states 'Side effects: credits points to the same Bearer key (no key rotation).' This is a purely additive operation. However, the annotations include destructiveHint: true, which directly contradicts the description's claim. This is a serious inconsistency that undermines transparency.

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?

The description is concise and well-structured, with a clear opening statement, an inputs list, a side-effects note, and a success return note. Every sentence adds value and there is no unnecessary verbosity.

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?

The description covers the inputs, side effects, and success response, and mentions that the return shape depends on upstream. It provides sufficient context for an agent to understand when and how to invoke the tool. However, the contradictory destructiveHint flag in the annotations leaves a completeness gap, preventing a perfect score.

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 already provides 100% coverage for both parameters, each with a description. The tool description simply restates the same information (quote_id from PAYMENT-REQUIRED, payment_signature_b64 as base64 JSON) without adding new semantics. With full schema coverage, a baseline of 3 is appropriate.

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 clearly states the tool's purpose: 'Top up points for the CURRENT Bearer key using x402 proof.' It uses a specific verb ('top up'), identifies the resource ('points for the current Bearer key'), and mentions the method ('x402 proof'). This distinguishes it from sibling tools like get_x402_quote and get_account_balance.

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 provides clear context: it says the quote_id is returned by PAYMENT-REQUIRED or /api/v1/x402/quote, implying the tool is used after obtaining a quote. It does not explicitly mention alternatives or exclusions, but the usage context is clear. A score of 4 reflects the absence of explicit when-not-to-use guidance.

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