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

Annotations only declare readOnlyHint=true and openWorldHint=false, so the description carries useful extra weight: it discloses the return payload (base64 MP3 with sample rate and voice used), the per-call character cap, and the cost model (2 credits, charged only on success). That covers the main behavioral unknowns for a paid generation call, though it says nothing about latency, timeouts, or failure modes.

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?

Four short sentences ordered by importance: what it does, what comes back, when to use it (with the alternative), and the cost. No filler and no redundancy with the schema beyond the unavoidable character limit.

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 steps in to describe the return shape and the cost, and it names the sibling to route to for a different need. For a 3-parameter generation tool with full schema coverage and read-only annotations, nothing an agent needs to call it correctly 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 100%, so all three parameters are already documented in the schema, giving a baseline of 3. The description repeats the 2,000-character limit but adds no meaning for `provider` or `voice_model` (e.g., when deepgram vs elevenlabs is preferable), so it does not rise above 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?

States a specific verb+resource ("Convert text to speech audio") and immediately distinguishes itself from the closest siblings by name: sound-generate for effects/music and, implicitly, the transcribe/stt family for the reverse direction. An agent can classify 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?

Explicit when-to-use ("spoken voice or narration") plus an explicit redirect for the adjacent need ("For sound effects or music use sound-generate"). The 2,000-character ceiling and credit cost also set scope conditions for the call.

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