l402-fetch

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

Annotations only signal openWorldHint and destructiveHint; the description carries the burden and does so well. It discloses that the tool manages credentials, pays automatically when autoPay is true and cost is within budget, retries, and returns different payment artifacts depending on wallet type. This goes far beyond the generic annotations and warns of spending behavior without contradicting 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 dense and front-loaded, with each sentence contributing to core behavior or routing. It is longer than strictly necessary—'Set autoPay to true for seamless access' partly repeats the schema—but the extra scenario-based guidance is earned rather than filler.

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 complex, spend-capable tool with no output schema, the description covers the high-risk and non-obvious payment paths: automatic payment, human-wallet returns, x402 verification via txHash, tier handling, and preview flow. It does not explicitly describe the normal successful fetch response body or exact retry/budget limits, but it provides enough context for correct invocation in the main scenarios.

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%, so the baseline is 3. The description adds value by explaining the behavioral effect of autoPay (automatic payment within budget), txHash (replays the request with X-Payment header), and how responses differ for human wallets vs x402 services. It does not add much for url, body, method, headers, or pubkey, but those are already well-described in the schema.

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 opens with a specific action: 'Fetch a URL with automatic payment handling' and enumerates the supported payment protocols (L402 Lightning, x402 on-chain, ecash and LUD-25). It also differentiates itself from siblings by routing tiered payments to l402-buy-credits and widget-host flows to l402-fetch-preview, so an agent can distinguish it without opening other tool definitions.

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 gives explicit if-then usage guidance: when a 402 response includes tiers, present pricing and use l402-buy-credits; widget hosts should call l402-fetch-preview first. It also explains when autoPay should be true and distinguishes human-wallet flows from x402 flows, which is strong practical routing guidance.

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