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

Beyond the annotations (which only flag non-readonly, open-world, non-idempotent), it discloses concrete behavior: the free-allowance/credit cost model, the browser requirement that an in-app browser blocks the microphone, link expiry via expires_in, and a 429 rate-limit error. This is exactly the kind of operational context annotations cannot carry.

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?

Purpose is front-loaded in the first sentence, followed by a compact enumeration of return fields and the error case. It is dense but each clause carries operational meaning; only the return-field list is somewhat heavy given an output schema already exists.

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 zero-required-param creation tool with an output schema, the description still supplies everything an agent needs: purpose, the meaning of each returned link, expiry semantics, the browser caveat, and the rate-limit error. Nothing material 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?

Schema description coverage is 67%. The description restates lang (de/en, default de) which the schema already documents, and says nothing about `name` or `mode`. With the schema doing most of the work and `mode` undocumented in both places, this sits at the baseline.

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 ('Start a new voicehook.ai voice call') and the title reinforces it. It is clearly distinguishable from siblings like join, leave, say, and status, which operate on an existing call.

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 conveys the call-creation flow implicitly: it produces human_url (the human opens it to start) and operator_invite_url (the agent's link for join), which tells the agent this precedes join. However, it never states explicit when-not-to-use conditions or named alternatives for edge cases.

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