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

Goes well beyond the annotations by disclosing the credit formula (ceil(characters/20), minimum 1) and the synchronous rendering behavior with an output_urls result, which matters for an agent planning retries or cost. It hedges with 'usually returns immediately', implying possible latency, but doesn't explain what happens in the slow case despite the idempotency_key parameter existing for retry handling.

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 tight sentences, front-loaded with the core conversion action, then cost, then execution behavior. No filler and nothing redundant with the schema.

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 paid, 7-parameter generation tool with no output schema, the description usefully covers cost and return shape, but it leaves most tuning parameters unexplained and doesn't clarify what happens when rendering isn't immediate. Adequate but with 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 only 14% (just idempotency_key), so the description must carry the load for 7 parameters. It explains voice_id's sourcing via list_voices but says nothing about text, speed, model_id, stability, or similarity_boost, leaving five parameters undocumented in both places.

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+resource ('Convert text to speech') with the required input (voice_id) called out, which cleanly distinguishes it from siblings like generate_image, generate_music, and generate_sound_effect. An agent can pick this tool without opening the 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?

Usage is implied by the purpose, and it routes the agent to the sibling list_voices for picking a voice_id, which is useful. However, it never states when to prefer this over alternatives such as generate_sound_effect, nor any preconditions or exclusions.

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