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

Annotations give readOnlyHint=false, destructiveHint=false, openWorldHint=true, and the description supplies the missing context: the call costs 15 points, explaining the non-read-only flag. It also discloses the phone_ref null case, the phone_ref_unavailable_reason field, and the field fallbacks to show the user, none of which the annotations reveal.

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?

Purpose and returned fields are front-loaded in the first sentence, followed by the location convention, the phone_ref/call_business relationship, and the cost. Every sentence carries unique information and none is redundant.

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 4-parameter lookup tool with an output schema and partial annotations, the description covers everything an agent needs to invoke and route correctly: the location convention, the cost, the phone_ref handoff to call_business, and the null-case fallback. Return-value explanation is unnecessary given the output schema, yet the phone_ref semantics still add value.

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 the schema already documents cid, name, language, and location. The description reinforces the location constraint and adds the same-location convention, but that repeats what the schema property description already states, so it adds little beyond the baseline.

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 and resource ('Full details for one place') and enumerates the returned fields (phone, hours, rating, website, booking link). It explicitly positions itself as the follow-up to search_places, so an agent can distinguish it from that sibling without opening either schema.

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?

Clearly implies the sequencing ('one place from search_places', 'Pass the same `location` you searched with') and routes the agent to call_business via the phone_ref handle, with an explicit fallback when phone_ref is null. It stops short of an explicit 'use this only after search_places' statement and names no when-not condition, so it is strong context rather than a full decision rule.

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