buildx_prune

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

The description discloses critical behavioral traits beyond the annotations: it always passes `--force` because MCP lacks an interactive prompt, directly addressing the destructive nature. It also explains the return format. This adds significant value beyond the destructiveHint and idempotentHint annotations.

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 well-structured and front-loaded: a one-line purpose, a prominent destructive warning, then a clean parameter list. Every sentence adds essential information, with no fluff or repetition of schema defaults.

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?

Given the tool's complexity (7 parameters, nested objects, no output schema), the description is remarkably complete. It covers the return structure, warns about forced behavior, provides parameter examples, and mentions the companion tool buildx_du. Nothing critical is missing.

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 has no parameter descriptions (0% coverage), but the description compensates fully by documenting every parameter with concise explanations and concrete examples (e.g., filters as JSON, space values as strings like '10GB'). This gives the agent the semantic context needed to populate parameters correctly.

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 'Remove BuildKit cache entries.' This clearly states the tool's purpose with a specific verb (Remove), a specific resource (BuildKit cache entries), and differentiates it from sibling tools like buildx_du (which inventories disk usage) and buildx_remove (which removes builders).

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 provides a clear usage guideline by recommending 'Pair with buildx_du first to inventory what would be removed.' This tells the agent when to use this tool relative to a sibling. However, it does not explicitly discuss when NOT to use it or mention alternatives, so it stops short of a 5.

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