Set a media item's description

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

Beyond the annotations, the description adds important behavioral context: the restriction to app-uploaded media and the clearing behavior on empty string. It does not contradict the annotations and provides useful detail about how the operation behaves.

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 short sentences front-load the core action, then add the key constraint and the clearing behavior. Every sentence earns its place and there is no filler.

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 simple mutation with rich schema coverage, the description covers the operation's scope and special empty-string behavior. It does not describe error cases or return values, but the annotations already convey the safety profile and the schema covers parameter semantics.

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 three parameters. The description adds real-world context about the description field and the app-uploaded scope, but it does not need to repeat parameter details.

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 and resource: 'Write the description shown under a photo or video in Google Photos.' It also distinguishes this tool from related media tools by stating it only works on media this app uploaded.

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 gives a clear scope condition: only media this app uploaded, which helps an agent decide when not to use it. It also clarifies that an empty string clears the description, but it does not explicitly name alternatives; no sibling tool performs the same function, so the exclusion is sufficient.

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