Fetch a paid URL (x402 or MPP), paying if required

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

No annotations provided, so description carries full burden. It explains the payment process (signs USDC payment, subject to spend caps and allowlist) and what the LLM sees. However, it does not disclose error handling for payment failures or rate limits.

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?

Four sentences, each earning its place: main purpose, 402 handling, restrictions, and LLM visibility. No filler, front-loaded with the core action.

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?

Given no annotations and no output schema, the description explains the return value ('response body') and hides wallet details. Missing error scenarios and redirect/timeout handling, but comprehensive for a payment tool.

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 100%, and description adds no new meaning beyond the schema. The description's parameter descriptions ('Full URL of the paid endpoint', 'HTTP method (default GET)') are redundant with schema descriptions.

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 it makes HTTP requests to URLs that may require payment, handles 402 responses with x402 or MPP protocols, and returns the response body. This distinguishes it from siblings like pay.discover (for discovering paid endpoints) and pay.wallet_status (for wallet state).

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 implies use for URLs requiring payment but does not explicitly state when to use this tool versus siblings. It lacks guidance on when not to use it or alternatives like pay.discover for listing endpoints.

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