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

Beyond the annotations, the description discloses important behavioral traits: results are cached (consistent with idempotentHint), requires an API key, and notes that audio generation has real cost. This adds valuable context that annotations alone do not convey and aligns with the non-read-only, non-destructive hints. No contradiction found.

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 sentences, each with a clear purpose: the first states the core function and output, the second covers the primary input parameters, the third notes caching behavior, and the fourth explains the API key requirement and cost. No filler or redundancy; front-loaded with the main purpose.

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?

Despite having no output schema, the description tells you exactly what to expect ('playable audio URL'), covers the required input (text), key optional parameters, caching, auth, and cost. All five parameters are well-specified in the schema, and the description provides the missing operational context (cost, key) needed for a complete usage picture.

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 the schema already documents all five parameters in detail. The description adds only a small framing benefit (e.g., '50+ languages', 'optional voice/gender') but does not provide new semantic details beyond the schema's own parameter descriptions. This matches the baseline for complete schema coverage.

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 uses a specific verb ('Generate') and resource ('spoken-audio / text-to-speech') and clearly states the output ('playable audio URL'). It also scopes the content domain ('verse, prayer, or devotional'), distinguishing it clearly from sibling tools like get_verse or search_sermons, which are text-based.

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?

It provides clear context on how to use the tool by mentioning the BCP-47 language tag and optional voice/gender parameters. The cost and API key requirement give practical usage guidance, though it does not explicitly name alternatives or state when not to use this tool (no TTS alternatives exist among siblings anyway).

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