generate_and_merge_media

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

With no annotations, the description must cover behavioral traits. It reveals that the output is valid HTML and instructs the agent to display it in an HTML Artifact. This is helpful but could be more explicit about processing time or resource usage. Still, it adequately informs the agent of the output format and expected action.

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?

The description is concise and well-structured. It starts with a clear purpose statement, then breaks down parameters, and ends with a critical usage instruction. Every sentence provides valuable information with no redundancy.

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 tool's two parameters and the presence of an output schema, the description is complete. It covers input requirements, optional parameters, output format (HTML), and the required user-facing action. No gaps are evident.

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?

The schema has 0% description coverage, so the description must compensate. It explains 'source_media_url' as a publicly accessible URL to source media, and 'music_prompt' as an optional music description that defaults to generation by Gemini. This adds meaningful context beyond the schema's type-only definitions.

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 the tool's purpose: 'Generates a music video by combining AI-generated audio with the source image or video.' This is a specific verb+resource pair, and since there are no sibling tools, differentiation is not needed.

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 provides guidance on the optional music_prompt parameter, stating it can be omitted for Gemini to generate one. It also includes a crucial usage instruction: the output must be displayed via an HTML Artifact. However, it does not discuss when to use this tool versus alternatives (none exist) or any prerequisites beyond public URL accessibility.

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