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

The description adds meaningful behavior beyond the annotations: sending null clears the description, and the value affects downstream campaign rendering. It also scopes the mutation to the description only. Annotations already indicate a non-read operation with idempotent and non-destructive hints, so no contradiction exists.

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 tight sentences: the action, a concrete motivating example, null behavior, and a scope boundary. Nothing is wasted and the key behavior is front-loaded.

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 two-parameter metadata update with an output schema and relevant annotations, the description covers purpose, null semantics, and what cannot be changed. No critical information is missing for an agent to invoke it correctly.

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 documents the description parameter, but the description adds real meaning: it explains the purpose of the text, provides a concrete example, and clarifies that null removes the current value. The id parameter is self-evident, and the description's example compensates for the incomplete 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 states a specific verb and resource: 'Say what a file shows' — i.e. update a file's description. It clearly differentiates from sibling media tools by noting 'Nothing else about a file can be changed here,' so an agent knows this is not a rename, move, or metadata edit. The scope is precise and actionable.

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 gives clear context for when to use it: describing what a file shows, especially for base images so campaign renders stay consistent. It also states what it is not for ('Nothing else about a file can be changed here'). It does not explicitly name sibling alternatives, but the exclusion is strong enough to route an agent correctly.

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