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

Annotations already cover the safety profile (readOnly, idempotent, openWorld, non-destructive), and the description layers on context those annotations cannot express: Google rich business details are disabled, missing fields mean unavailable rather than closed/absent, and cached optional details may be stale. These are exactly the failure modes an agent would otherwise misread.

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?

Four short sentences, ordered purpose first, then the negative routing, then two interpretation caveats. No filler, and the most decision-relevant constraint (what this tool cannot answer) is front-loaded.

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 still tells the agent which fields to expect, how to interpret absent fields, and that cached values may be stale. Nothing needed to call or interpret this tool correctly is missing.

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 100%, so both place_id and language are already documented in the schema, and the description correctly ties place_id back to places_search output. It adds nothing about the language parameter's effect on returned data, so the baseline 3 is appropriate.

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 (look up) and resource (place ID) and enumerates the exact fields returned: name, address, map URL, coordinates, photos, timezone. It also positions itself relative to the sibling places_search by scoping its use to IDs already obtained there.

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 trigger ('when missing from places_search') and explicit exclusions naming six question categories (opening-hours, open-now, price, website, phone, rating) the tool must not be used for. This is a rare case of a description telling the agent both when to use it and when not to.

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