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

Annotations cover readOnly and openWorld, but the description adds substantial unseen context: the exact price (0.005 USDC on Base), the payment scheme (EIP-3009 transferWithAuthorization), the header names for v1/v2, and the failure-billing rule ('only charged if extraction succeeds'). That billing-on-success semantics is exactly the kind of behavior an agent cannot infer from annotations.

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?

Front-loaded with purpose and output, then the payment mechanics in a compact sequence. The payment clauses are dense but each carries necessary information; no filler, though the x402 detail is heavier than a casual reader needs.

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?

With no output schema, the description enumerates the returned fields itself, and it closes the loop on cost, payment flow, and failure charging. Nothing an agent needs to invoke this correctly is missing.

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 both parameters are already documented; baseline would be 3. The description exceeds that by explaining the role of x_payment in the two-step flow (first call omits it, second carries the signed payload), which adds meaning beyond the field's own schema text.

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?

Specific verb+resource+output: 'Fetch a public web page and return clean Markdown of its main content', with the return shape (title, byline, excerpt, markdown) enumerated. Even without siblings, an agent knows exactly what this does and what it gets back.

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?

Gives an explicit two-step protocol: call without x_payment to obtain requirements, then re-call with the signed payload. This is clear operational context, though it stops short of stating when-not to use it or any failure/fallback alternative.

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