x402_fetch

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

With no annotations, the description carries the full behavioral burden. It does disclose genuinely important traits: deterministic spending caps and automatic EIP-3009 payment authorization on Base L2, which tells the agent this tool can spend real funds. But it omits critical follow-through — what happens when the cap is exceeded, whether the payment is idempotent or retryable, and whether the response includes a receipt.

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?

A single dense sentence, front-loaded with the verb and the strongest distinguishing detail (paid-endpoint support). The adjective 'Safely' is somewhat promotional but the rest of the wording is specific. Nothing is wasted.

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 four-parameter tool with full schema coverage and no output schema, the description is close to complete on inputs. The gap is on the payment lifecycle: how caps are configured or discovered (a sibling exists for this), and what a caller gets back on a paid versus free fetch, which an agent spending money would want to know.

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 100%, so url, body, method, and headers are already well documented in the schema itself. The description adds no extra meaning about parameter behavior, so the 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?

Names a specific verb (fetch) and resource (HTTP endpoints), and scopes it as covering both free and x402-paid resources. It is distinguishable from the siblings (budget check, safe transaction, audit log), though it never explicitly contrasts itself with them.

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 phrase 'free or x402-paid' implies the tool works for both unpaid and paid endpoints, which is useful scoping. However, there is no explicit when-to-use guidance, no mention of checking the budget first via x402_get_budget, and no guidance on what to expect when a spending cap is reached.

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