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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely useful behavior beyond them: hard truncation caps (up to 50 cars per family, up to 30 per city), the metadata.truncated signal, and that an unknown id errors out.

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?

One dense paragraph, front-loaded with the core action and then the per-type detail. Every clause carries information, though the inline parenthetical enumerations make it heavier than it needs to be for a single-parameter tool.

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?

An output schema exists, so return values need not be explained, yet the description still sketches what each document type yields. Combined with the truncation and error semantics, an agent has enough to call this correctly; only auth/permission expectations are unstated.

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 id format is already fully documented in the schema, giving a baseline of 3. The description adds real semantic value on top: "Pass the id unchanged" and the failure mode of an unknown id, which the schema does not state.

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 (the full document) and scopes it to an id from search, then enumerates the four document shapes and what each contains. It is clear, but it never contrasts itself with the overlapping siblings get_company and get_news_article, so an agent cannot fully disambiguate on the name alone.

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?

"Use this when you have an id from search and need the details of that one result" gives a clear trigger condition and even the follow-up action (cite its url). There is no explicit when-not or alternative-tool statement, which is the only gap.

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