Place Outbound Call (SIP Trunk)

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

Describes the async behavior (returns immediately, does not wait for call to finish), the return JSON structure, and error handling. Annotations already indicate it is a mutation (readOnlyHint=false), and the description adds more context without contradiction.

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?

Well-structured with a clear purpose, then args and returns sections. Every sentence adds value, no fluff. Front-loaded with the critical async behavior.

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 tool with no output schema, the description explains the return format and necessary follow-up. It covers prerequisites (agent must allow overrides) and references sibling tools appropriately. Comprehensive for an async initiation tool.

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% with parameter descriptions, but the description adds extra context for parameters like dynamic_variables (variables for agent's prompt) and prompt_override (requires agent to allow overrides). This goes beyond the schema, though the schema already does well.

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 clearly states 'Place an outbound telephone call via an ElevenLabs agent over a SIP trunk' with specific verbs and resources. It distinguishes from siblings by noting it initiates the call and returns immediately, whereas other tools retrieve reports or wait for completion.

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 states the call starts and returns immediately, with a clear instruction to follow up with elevenlabs_wait_for_call_completion using the returned conversation_id. Also provides error handling guidance. Does not explicitly mention when not to use, but the context is clear enough.

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