Place the call (requires confirm: true)

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

Annotations only say readOnlyHint=false, openWorldHint=true, destructiveHint=false. The description adds the traits that actually matter here: it costs money, it rings a real phone, and it must not be fired until a human approves the preview. That is real side-effect and safety context the annotations do not convey.

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?

Three sentences, front-loaded with the step-of-workflow marker and the 'Step 2 of 2' framing first, then cost/side-effect warning, then the parameter contract. No filler.

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?

With no output schema, the description could note what a successful placement returns (e.g. a call id for get_call/end_call), which it omits. Everything an agent needs to invoke it correctly and safely, however, is present.

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 0%, so the description carries the burden, and it does explain both parameters: previewId originates from prepare_call, and confirm must only be set after explicit user approval. It stops short of stating confirm's default behavior or what a false confirm does, so it is strong but not exhaustive.

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 ('Places the previewed call') and immediately positions itself in a two-step workflow, distinguishing it from the sibling prepare_call ('Step 2 of 2', consumes 'previewId from prepare_call'). An agent can tell this apart from prepare_call, estimate_cost, or get_call without opening a 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?

Gives an explicit precondition (previewId from prepare_call), an explicit gating rule (confirm:true set ONLY after the user has explicitly approved the number, language, goal and estimated cost), and implicitly routes the agent to the step-1 alternative. Nothing about when-to-use is left to inference.

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