set_icon

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

With no annotations provided, the description carries the full burden. It discloses that the server fetches, validates, and stores the image, states that execution is immediate, and notes reversibility. This gives a reasonable picture of behavior, though it does not mention failure handling or whether the existing icon is overwritten.

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 two concise sentences with no fluff. The primary action is front-loaded, followed by crucial behavioral details. Every sentence contributes new information.

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 tool with no output schema, the description covers the essential aspects: the action, URL constraints, server-side process, execution timing, and reversibility. It lacks details on return values or error conditions, but these are not critical for such a straightforward update operation.

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 baseline is 3. The description adds meaningful context beyond the schema by specifying that the icon URL must be publicly reachable and https, and that the server validates the image. This reinforces and enriches the schema definitions for both parameters.

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 function: "Sets an app's icon from a publicly reachable https URL." This identifies the exact action and resource, and the additional detail about server-side fetching and validation further clarifies scope. It is easily distinguished from sibling tools like configure_app or set_permissions.

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 implies usage context (e.g., when you need to update an app icon from a URL) but does not explicitly state when to prefer this tool over alternatives or mention any exclusions or prerequisites. The reversibility note is useful but not a substitute for explicit when-to-use guidance.

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