Guide a call in progress

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

Annotations already cover the safety profile (readOnly=false, idempotent=false, openWorld=true, destructive=false), and the description adds genuinely non-structured behavior: it acts immediately, silent:true downgrades it to a background note applied when relevant, and it returns a conflict error after the call ends. It does not cover auth/permission expectations or whether repeated sends accumulate, so it stops short of a 5.

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 tight sentences, with the core behavior front-loaded before the silent mode nuance and the sibling-routing note. No sentence is filler and the examples earn their space by clarifying what 'guidance' means.

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?

There is no output schema, so the description carries the return-side burden; it discloses the conflict error rather than a success payload, and no success return shape is described. Combined with the naming of sibling alternatives, this is nearly complete for a 3-parameter write tool.

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 33% (only callId is documented in the schema), so the description must compensate. It does explain silent's semantics well, but the required text parameter is only implied through examples, and no length/format guidance (e.g., the 2000-char cap) is conveyed.

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 opens with a specific verb+resource+state: passing guidance to a voice during an in-progress call or meeting, with concrete examples. It explicitly distinguishes itself from end_call and transfer_call_to_me, so an agent can route correctly without opening any 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?

It clearly states the enabling condition (call still in progress), the two named alternatives for adjacent intent (end_call, transfer_call_to_me), and the failure mode once the call has ended. The one gap is that silent: true overlaps conceptually with the sibling save_call_note, and the description never tells the agent when to prefer one over the other.

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