Retrieve a call

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

Annotations already declare readOnlyHint=true, so the safe-read profile is known. The description adds meaningful context beyond annotations: it requires scope 'calls:read' and explains failure_code semantics (Q.850 causes) and failure_reason guidance. This goes beyond the baseline safety hints without contradicting any annotation.

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?

The description is efficiently structured: first paragraph lists the full contents, second paragraph addresses failure specifics with useful codes. The Q.850 code list is slightly verbose but relevant for interpreting failure_code. Every sentence earns its place.

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 enumerates all expected return fields and failure fields, plus auth requirements. The input is covered by the schema. For a single-get tool, this is complete enough for an agent to call it correctly and interpret the response.

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?

The input schema fully documents the only parameter id with 'The call id (not the session_id),' providing clear semantics. The description does not add any additional parameter-level meaning, so baseline 3 is appropriate given 100% schema coverage.

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 title 'Retrieve a call' and the description 'The full call record: status, duration, cost_micros, recording_url, summary, transcript, transfers, and any provider errors' clearly state a specific verb and resource. It distinguishes itself from siblings like get_call_transcript by enumerating all fields returned.

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?

Usage is implied through the description of returning the full call record and failure diagnostics, but no alternatives are explicitly mentioned. It does not say when to use this instead of get_call_transcript or list_calls, nor when to avoid it. Thus guidance is present but left to inference.

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