Call

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

Annotations declare the safety profile (destructive=false, idempotent=true), and the description adds substantial context beyond them: a greeting is spoken on start, the rules of the call are returned, and hangup can be triggered by the user ('hang up', 'bye Claude') or by long silence. Remaining gap: it does not say what happens if start is invoked while a call is already active, which is exactly where idempotentHint=true would matter.

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 definition, then actions, then in-call routing — good ordering with no filler sentences. The 'like a phone call, until they hang up' clause is slightly verbose but does real semantic work by conveying the open-mic model, so the cost is minor.

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?

One required enum parameter, annotations covering safety, no output schema to explain — the description covers the full lifecycle (start, in-call, implicit and explicit end) at the right level of detail for a tool this small. Nothing an agent needs to invoke it correctly is missing.

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?

With one enum parameter at 100% schema coverage, the baseline is 3; the description earns above that by adding outcomes the schema omits — start returns the rules of the call, and end may occur without an explicit call. The schema's own enum text ('take the mic and greet the user') is thinner than the description's explanation.

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 specific verb and resource pair ('Start or end a call') and immediately defines the resource in operational terms (hands-free, mic stays open, user talks freely). An agent can distinguish this from 'say' and 'listen' without opening either schema, since the description frames those as in-call primitives.

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?

Gives explicit when-to-use for each action ('action start takes the speaker and microphone', 'action end hangs up') and routes in-call behavior to the correct siblings: 'During the call, speak with say and hear the user with listen.' It also lists the implicit conditions under which the call ends, so the agent knows ending is not solely its job.

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