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

Annotations already cover read-only/idempotent/open-world/non-destructive, and the description adds a lot on top: partial failures don't fail the whole call, metering is one call per URL against a 50/day free bucket shared with web_fetch, then 1 credit per URL over x402, max 5 URLs, no API key. This is unusually rich behavioral disclosure.

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, then labeled 'When to use', 'Do not use', 'Returns', and metering sentences. Dense but every clause is load-bearing; only the metering detail is slightly verbose for a description field.

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?

No output schema exists, and the description compensates by enumerating the return object fields (ok, count, ok_count, results with url/final_url/status/title/engine/chars/snippet, took_ms, _metering). Combined with metering and partial-failure semantics, an agent has everything needed to call and interpret it.

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, but the description adds practical meaning: it explains the ~1200-character snippet length (the max_chars default) and the 5-URL cap in terms of triage use. It does not document the format enum's effect beyond what the schema says.

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 (fetch) plus resource (up to 5 public URLs) and the exact output shape (title, engine, ~1200-char snippet), framing the goal as triage. It explicitly differentiates itself from web_fetch and web_map by name.

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 when-to-use scenario (search returned several candidates, want a first pass) and a named follow-up tool (web_fetch for full text), plus a 'Do not use' clause routing crawls to web_map. Both positives and exclusions are covered.

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