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

Annotations declare openWorldHint=true and destructiveHint=false, which the description reinforces with the concrete default (fill_empty_only, does not overwrite agent-supplied fields) — a real behavioral guarantee beyond the annotation. It also discloses the not_configured failure mode when GOOGLE_PLACES_API_KEY/GOOGLE_MAPS_API_KEY is absent and a $0.15 cost, though it never says what happens when fill_empty_only is set false (i.e., whether existing values are overwritten).

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 tightly packed sentences, front-loaded with the core action and default behavior before the failure mode and cost. The parenthetical field list and API-key aliases add density but each element carries information an agent needs.

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 an output schema present, return values need no explanation, and the description still covers the default write policy, the external-dependency failure mode, and cost. The main gap is the behavior under fill_empty_only=false and role of business_contact_id, but overall it is sufficient to invoke the tool correctly.

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 only 40% across 5 parameters, so the description must compensate. It does explain the important fill_empty_only flag (default and non-overwrite semantics) that the schema leaves undocumented, but place_id, business_contact_id, and the idempotency alias pair receive no additional meaning from the description.

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?

Names a specific verb (enrich/fill) and resource (saved place card) and enumerates the fields it populates (hours/address/phone/website), so the agent knows exactly what the tool produces. It does not explicitly name a sibling like update_place or create_place to route against, so the differentiation from those tools is inferred rather than stated.

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?

"Optional Google Places fill" signals when the tool is appropriate (supplementing an existing place card with external data), and the default fill_empty_only implies the safe path. However, no alternative tool is named and there is no explicit when-not guidance, leaving the agent to infer when a manual update_place is preferable.

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