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

Annotations already declare openWorldHint=true and non-idempotent/non-destructive behavior. The description adds that it 'returns their answer,' clarifying that this is a synchronous exchange rather than a fire-and-forget message, but it says nothing about blocking duration, failure modes, or secret/auth handling.

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?

Two short sentences, front-loaded with the action and immediately followed by the return behavior. Efficient, though it may be too terse for the tool's complexity.

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 open-world tool with no output schema, the description gives only the minimum: that it returns the other party's answer. It omits how the exchange completes, whether the call stays open, and how errors surface, leaving gaps for an agent orchestrating a conversation.

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 75%, with the 'to', 'secret', and 'call_token' fields well documented in the schema and only 'message' bare. The description adds nothing about parameters, but the schema does most of the work, so a baseline 3 is warranted.

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 ('say') plus resource ('the next thing on a call') and constrains it to calls you started, which implicitly separates it from answer_call or call. It does not explicitly name the sibling alternatives, so an agent must infer the boundary rather than being told.

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?

'On a call you started' implies the prerequisite (you must have initiated the call and hold a call_token), but there is no explicit when-to-use rule or comparison against answer_call, leave_message, or listen. Usage is inferable rather than stated.

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