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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false. The description reinforces the closed-world constraint with "No arbitrary URLs are fetched," which adds concrete specificity beyond the flag, but reveals nothing further about return format or failure behavior.

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?

Two short sentences, zero waste, with the accepted-input scope front-loaded and the negative constraint immediately following.

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 one-parameter read tool with full annotation coverage, the definition supplies the precondition, the accepted inputs, and the URL restriction. Only the return shape is unaddressed, which is a minor gap given no output schema exists.

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 carries the burden for the single 'id' parameter. It usefully explains that the value is either a known document ID or an exact canonical URL, which is meaningful semantics the bare string schema does not convey.

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 (a known document ID or exact canonical URL), which is distinct from the exploratory sibling 'search'. It implies the discovery-vs-retrieval distinction without fully naming search as the counterpart.

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?

"returned by search" establishes the precondition that an ID/URL must already be known, and the second sentence rules out arbitrary URLs. It stops short of an explicit "if you don't have an ID yet, call search first" routing statement, but the context is clear.

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