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

Annotations already declare destructiveHint/readOnlyHint/idempotentHint, and the description adds real context beyond them: the exact $4.00 charge, the confirm gate, the site-fetch-and-generate side effect, and the crucial clarification that the server never settles payment itself. It stops short of saying whether the charge is refundable or where webmcp.js is written.

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 'DESTRUCTIVE' and the price, then the side effect, then the confirmation rule – the most decision-relevant facts come first. The 'POST /x402/webmcp-upgrade JSON {url, notes?}' fragment partly duplicates the schema and could be trimmed.

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 paid, destructive mutation tool with a fully documented 4-parameter schema and no output schema, the description covers cost, confirmation, side effect, transport, and payment responsibility. Nothing an agent needs to decide whether to call it 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 description coverage is 100%, so the schema already explains url, notes, confirm, and the full payment/x402 challenge flow. The description only restates the endpoint shape and the non-settlement caveat, adding little semantic detail beyond 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?

States a specific verb and resource ('places a paid WebMCP upgrade order'), plus the concrete side effect ('Fetches the site and generates webmcp.js') and the endpoint. An agent can immediately distinguish this from the read-only sibling check_webmcp.

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?

Explicit gating instruction: 'Confirm with the user before calling' plus the confirm parameter requirement, which tells the agent exactly when it may proceed. It doesn't name check_webmcp as the non-paid alternative, so there is a small gap in alternative routing.

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