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

With no annotations at all, the description carries the full burden and does well: it discloses that the call is paid ($0.01 USDC on Base or Solana), that no account or API key is needed, and that failed calls are not charged — three non-obvious behaviors an agent needs before spending money. It omits rate limits, redirect/timeout behavior, and how non-2xx responses are treated, which keeps it short of a 5.

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 short sentences, with the cost caveat ('Paid.') and the core action front-loaded — exactly what an agent should see first. The trailing endpoint URL is arguably redundant in an MCP context but is not harmful. No filler sentences.

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?

There is no output schema, so the description must characterize the return, and it does: HTTP status plus response headers. Pricing, payment rails, and auth requirements are all covered, which is the important surface for a paid tool. Edge cases such as redirects, timeouts, and non-success responses are the remaining gap.

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% and the single 'url' parameter is already documented as 'Page URL, http(s)'. The description adds no syntax, format, or constraint detail beyond that. Baseline 3 applies when the schema does the explanatory work.

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: 'Fetch a URL and get the HTTP status and response headers.' An agent can distinguish this from body-returning siblings like buy_fetch_fetch or buy_fetch_fetch-html by the word 'headers'. It stops short of naming those siblings explicitly, so the differentiation is inferred from the title rather than stated.

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?

Usage is implied rather than stated: the tool is for cases where only status and headers matter, but the description never says so or contrasts it with the other fetch/scrape siblings. There are no exclusions or preconditions beyond the implicit need for a URL. An agent must infer when to prefer this over a full-page fetch.

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