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

Beyond the annotations, the description discloses billing behavior ($1 covers the first 2 minutes; demo lines and unanswered calls are free) and the post-call state: get_call returns ended_reason "you_hung_up" and a summary. These are valuable behavioral details that annotations alone do not provide.

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 action is front-loaded in the first sentence. The remaining sentences cover usage, cost, and postcondition without repetition or filler. Every sentence earns its place.

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 destructive one-parameter tool with annotations and no output schema, the description is complete. It covers when to use it, the billing implication, and what get_call will show afterward. An agent has enough information to invoke it correctly.

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?

There is only one parameter, and schema description coverage is 100%, with the schema explaining that call_id comes from place_call. The description adds no further parameter semantics, so the baseline of 3 applies when the schema already carries the full burden.

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 and resource: "End a live call now." This clearly distinguishes the action from sibling tools such as place_call, stop_batch, or get_call. The agent can identify the operation 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?

It gives explicit usage conditions: "Use when the user asks to stop, or the call is clearly stuck." This tells the agent when the tool is appropriate. It does not name a direct alternative or state when not to use it, so it falls short of a 5.

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