List installed add-ons

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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false and destructiveHint=false, so safety is covered. The description adds genuine value beyond that: the underlying Supervisor endpoint (GET /addons) and two concrete error shapes (missing SUPERVISOR_TOKEN, HTTP <status>), which tell the agent how failures manifest. It stops short of describing pagination or rate limits, but for a read-only list that is minor.

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?

Front-loads the action, then layers Use when / Not for / Returns / Errors in scannable blocks. Every sentence carries distinct information and none is redundant with the title.

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 zero-parameter read-only listing tool with a full output schema and complete annotations, the description covers purpose, selection guidance, and failure modes. The explicit Returns block slightly duplicates the output schema but does not detract from completeness.

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 tool takes zero parameters, so the baseline is 4. Schema coverage is 100% and there is nothing for the description to compensate for; the field list it provides pertains to output, not input.

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?

States a specific verb and resource ('List every installed add-on') and enumerates the projected fields, so the agent knows exactly what comes back. It also names the sibling it is not (supervisor_get_addon), making it trivially distinguishable from the other supervisor_* tools.

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?

Contains explicit 'Use when' and 'Not for' clauses, and routes the agent to the correct alternative ('use supervisor_get_addon') for the excluded case. Nothing about tool selection is left to inference.

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