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

Annotations already declare destructiveHint=true, idempotentHint=true, and openWorldHint=true, so the safety and repeat-call profile is covered structurally. The description adds only the 'you started' ownership constraint and says nothing about what happens to the remote party or the line state after ending.

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?

A single six-word sentence with the action front-loaded and zero filler. It is arguably clipped to the point of omitting preconditions, but no sentence is wasted.

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 three-parameter destructive tool with no output schema, the description covers the bare minimum and leans on the annotations and schema for everything else. It omits error/lifecycle behavior (call already ended, invalid token) and post-conditions, leaving clear gaps.

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 100%, with each of 'to', 'secret', and 'call_token' documented in the schema itself, so the baseline is 3. The description contributes no additional parameter meaning, which is acceptable given the schema does the work.

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 verb 'End' plus resource 'call' states the action unambiguously, and 'a call you started' narrows scope beyond a generic hang-up. It doesn't explicitly contrast with siblings like answer_call or call, but the operation is unmistakable.

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?

'a call you started' implies the precondition that only self-initiated calls can be ended, which is useful implied guidance. However, there is no explicit when-to-use, no mention of what to do if the call was never started or already ended, and no named alternative.

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