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

Annotations already cover safety (readOnly, idempotent, non-destructive, closed-world), yet the description adds real value beyond them: the required id provenance from search, the attribution obligation ('Keep the credits and link the url'), and an inline sketch of the response fields despite there being no output schema.

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 with no filler, and the core purpose leads. The phrasing of the attribution clause ('when you repeat numbers') is slightly garbled but still actionable.

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?

With no output schema, the description helpfully enumerates the return keys, but it does not explain what 'text' or 'metadata' contain or what happens when the id is unknown. Adequate for a one-parameter read tool, but not fully self-sufficient.

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 0% and the single 'id' property is an undescribed string, so the description must compensate. It does partially by stating the id comes from search, but gives no format, example, or failure behavior for an invalid id.

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?

The name 'fetch' is generic, and the description says it returns 'the 7-day forecast of a place id from search' while listing return fields {id, title, text, url, metadata} that read like a place record rather than a forecast. That internal tension leaves the actual resource ambiguous, and nothing distinguishes it from the sibling 'forecast' tool.

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?

'a place id from search' establishes a prerequisite: the id must come from the search tool, which is genuinely useful routing. However, it never says when to use this instead of 'forecast', 'places', or 'history', so the agent has no explicit selection rule among four plausibly overlapping siblings.

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