Modal MCP Server

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

With no annotations provided, the description carries the full burden and successfully discloses the output format ('Returns audio URL or base64') and default voice behavior. It does not mention rate limits, text constraints, or URL persistence, but covers the critical behavioral traits of the synthesis operation.

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?

Two concise sentences with zero waste. Front-loaded with the action verb, parenthetical clarifies default behavior, and second sentence discloses return format. Every word earns its place.

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?

Given the lack of output schema, the description appropriately specifies the return values (URL or base64). It adequately covers the 3-parameter tool's behavior despite missing annotations. Slightly incomplete regarding error handling or text length constraints, but sufficient for the complexity level.

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%, so the description appropriately does not redundantly explain 'text', 'speed', or 'temperature'. It adds valuable semantic context that the voice is fixed to 'Isaiah' (not configurable via parameters), which explains why no voice parameter exists in the schema.

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 ('Synthesize') with clear resource ('speech') and technology ('Modal F5-TTS voice clone'). It clearly distinguishes from siblings (modal_apps, modal_logs, modal_render) which handle infrastructure/management tasks rather than audio synthesis.

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?

The description mentions 'Isaiah voice by default,' implying expectations about output voice quality/style, but lacks explicit guidance on when to use this versus alternatives or prerequisites (e.g., text length limits). Usage is implied by the specific capability but not stated.

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