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

Goes well past the annotations (readOnly false, openWorld true, destructive false) by disclosing per-call blocking behavior (each use speaks and waits for the caller's reply), the mutation ordering for hang_up (message spoken first, then the call ends), the transient nature of moment, and a prompt-injection warning about caller content. No contradiction with annotations.

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?

Front-loaded with the core action and the call_id key handling, and nearly every clause carries operational information. The colon-chained, run-on sentence style makes it denser than it needs to be, slightly slowing extraction of the hang_up and moment rules.

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 covers what comes back (the caller's reply and the call_id token) and how to continue the interaction across turns. The only parameter not touched in prose is secret, which the schema describes fully as optional from get_line.

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 coverage is 100%, so the schema already documents moment, secret, call_id, hang_up and message. The description still adds real value: the call_id carries a '~token' suffix and the whole string must be reused verbatim, and hang_up/moment have observable ordering effects — details not in the schema text.

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 concrete verb+resource ('Pick up a call ... and talk') and anchors it to the sibling that produces the input (wait_for_calls). It distinguishes itself from hang_up and moment within the same description, so an agent can pick it apart from its neighbors without opening the 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?

Explicit sequencing rules: call only after wait_for_calls reports ringing, reuse the returned call_id for every later answer, use hang_up:true only when the call's job is done, and 'never in the turn that asks a question' — an explicit when-not. It also names moment:true as the alternative for the not-ready case.

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