Authorize an x402 payment before signing

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

The description is transparent about side effects and safety: it is a paid operation, uses sandbox credits, fails closed on conflicting carriers, and does not charge for malformed inputs or signing failures. This complements the annotations and goes beyond them.

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 verbose and repetitive. Key information is front-loaded, but the same concepts (before signing, unpaid call, alternative endpoint) are restated across multiple paragraphs, making it harder to scan quickly. A more compact structure would improve this score.

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 return type, failure mode, and alternative paths, and notes that an output schema exists. However, missing parameter semantics and some redundancy mean it does not fully contextualize all available inputs, especially for an agent deciding how to construct a valid request.

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 low (17%). Only 'payment' and 'policy' have inline descriptions; 'api_key', 'capability', 'ttl_seconds', and 'x402_payment' are not explained in the schema. The description adds partial context for 'api_key' and 'x402_payment', but 'capability' and 'ttl_seconds' remain unspecified, leaving agent understanding incomplete.

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: authorize an x402 payment before signing and return a credential. It specifies the verb 'authorize' and the resource 'x402 payment', making it distinct from siblings. Some redundancy and unusual phrasing ('PAID.') slightly reduce clarity.

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 explicitly says to call this immediately before signing an x402 payment envelope, mentions the need for payment, and distinguishes the paid path from a free identity-only alternative. It also notes fallback behavior when request metadata cannot be set, providing actionable when-to-use guidance.

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