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

Annotations establish the safety profile (not read-only, open-world, not idempotent, not destructive), and the description adds genuine behavioral detail beyond them: the two-step ring-then-dial flow, that the user speaks on the resulting outgoing call, and the important abort condition that no phone answering means the destination is never dialled. The 'Pro plan' note also flags an entitlement requirement.

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 core ring-then-dial behavior is front-loaded in the first two sentences, and there is no wasted filler. The subsequent short declaratives ('The user speaks on it. Pro plan.') are a bit staccato, but each carries a distinct fact.

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 two-parameter call-placement tool with no output schema, the description covers the execution flow, the abort condition, the plan requirement, and how the result manifests. It does not address permissions on identity_id or call failure modes beyond 'no answer', which keeps it just short of complete.

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 destination and identity_id are already documented in the schema. The description references the destination concept ('dials the destination') but adds no format, validation, or identity_id semantics beyond the schema, so the baseline 3 applies.

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 description gives a specific verb and mechanism: it rings the user's phones, then dials the destination into the answered conversation, producing an outgoing call. This is clearly distinct from siblings like control_call or quote_call. It stops short of explicitly naming what it is not, so it earns a 4 rather than a 5.

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?

The only usage signal is the terse 'Pro plan' prerequisite, which is useful but not framed as a condition for choosing this tool. There is no statement of when to use request_call versus alternatives such as control_call, request_speak, or quote_call, and no exclusions.

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