Place an outbound call

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

Goes well beyond the annotations by defining success semantics ("ACCEPTED/QUEUED ... does NOT mean the call connected"), disclosing the real-world side effect of dialling a live number, the idempotency-key replay behavior, the answer_url dependency, and the enforced server policy (country/prefix caps, concurrency, balance). The replay note does not contradict idempotentHint=false: the tool still dials per key, which the description makes clear.

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 action, endpoint, and required parameters, and nearly every sentence carries actionable information. The final policy sentence is a dense enumeration that could be tightened, keeping it just short of a 5.

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, money-spending, open-world mutation with ten parameters and no output schema, the description supplies everything an agent needs: preconditions, success interpretation, follow-up, retry/idempotency rules, and policy constraints. Nothing material is left for the agent to infer.

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 100%, so the baseline is 3; the description adds genuine meaning on top by stating that `from` must be an active number on the account, that `answer_url` is only conditionally required (server default fallback), and that confirm is a user-approval gate rather than a plain flag. It doesn't add much for the remaining optional parameters like hangup_url, ring_timeout, or answer_method, which is why this lands at 4 rather than 5.

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 ("Initiate ONE outbound call through Vobiz (POST /Account/{auth_id}/Call/)") and emphasizes the single-call scope. It is unmistakably distinct from siblings like list_live_calls, get_call_status, and end_call, which an agent can rule out without reading any 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?

Explicitly covers when to use it (after the user has approved this exact call), when not to ("Never call this twice for the same intent"), and the alternatives for the unknown-outcome case (list_live_calls / list_call_records). It also names the correct follow-up tool, get_call_status, with the exact argument to pass.

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