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

With no annotations at all, the description carries the full load and does well: it discloses the return format (text verbatim), a side artifact (Ed25519 receipt attesting fetch time and bytes), a hard size limit (1 MiB), and failure behavior (refusals carry an `error` and nothing is fetched). Gaps remain on permissions/auth, rate limits, and how non-text payloads are handled, but the safety-relevant profile is largely covered.

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?

Three tight sentences, each earning its place: scope first, then return value and receipt, then failure mode. No filler and no redundancy with the title.

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 single-parameter fetch with no annotations and no output schema, the description covers input domain, output shape, limits, and error behavior — enough to call it correctly. Missing only operational details such as authentication or throttling, which are unlikely to block a first invocation.

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 0%, so the description must compensate, and it does by defining which URL schemes are valid inputs — the single most important semantic for this one-parameter tool. It does not clarify whether the scheme prefix is mandatory or how such URLs are addressed, leaving a small residual ambiguity.

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) and resource (one URL) plus an explicit scope: networks HTTP agents cannot reach, enumerated as gemini://, gopher://, ipfs:// and ipns://. The scoping makes it trivially distinguishable from the only sibling (about) without opening either schema.

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 scheme whitelist functions as a clear when-to-use condition: use this only for URLs on non-HTTP networks, and the 1 MiB / text-only notes imply what is outside scope. It stops short of naming an alternative tool or stating what to do for ordinary http(s) URLs, so exclusions are implied rather than explicit.

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