buildx_list

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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral detail beyond that: it states that the tool raises RemoteFailureError on CLI failure, specifies the return format ("One dict per builder (parsed from `--format '{{json .}}'`)"), and discloses truncation handling (dropping last partial record if MAX_CLI_OUTPUT_BYTES is exceeded). These are non-obvious traits that materially affect invocation and result interpretation.

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 compact and front-loaded: the primary action appears in the first sentence, followed by differentiation, error behavior, and return details. Each sentence carries distinct information without redundancy. The use of a Returns section is clean and keeps the main body concise.

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 list tool, the description is fully complete. It explains the output shape, the error condition, and how truncation is handled. It also points to relevant siblings. There is no missing information an agent would need to invoke or interpret the tool 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 input schema is an empty object (0 parameters), so there is nothing for the description to explain. Per the rubric, the baseline for 0 parameters is 4. The description does not add or need to add parameter semantics since none exist.

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 opens with a precise statement — "List builder instances" — which is a specific verb+resource pair. It further differentiates from siblings by calling it a "Machine-parsed view of every builder" and explicitly naming `buildx_inspect` (for one builder's human-readable detail) and `buildx_use` (to switch the default). This makes the tool's role unmistakable relative to its siblings.

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 explicitly directs when to use alternatives: "use `buildx_inspect` for one builder's human-readable detail and `buildx_use` to switch the default." This provides clear context on when this tool is appropriate and when a sibling is preferable, leaving no ambiguity for the agent.

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