system_df

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

Annotations already declare readOnlyHint=true and destructiveHint=false, covering the safety profile. The description adds a behavioral warning about large payloads on busy hosts and specifies the output structure (dict with given keys), which is useful beyond the 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 efficiently written: a clear first sentence defines the purpose, followed by usage guidance and a warning, and a compact 'Returns' section. It's not overly verbose, though the Returns section could be integrated more tightly; still, every sentence contributes value.

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 read-only, no-parameter tool with no output schema, the description fully covers what the agent needs: what it does, when to use it, what it returns (including the dict keys). Nothing essential is missing for a correct invocation.

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 has zero parameters, so the schema is trivially complete (100% coverage). The description doesn't need to explain parameters; the baseline of 4 applies because there is nothing to document, and the description adds no parameter-related information but it's not required.

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: 'Summarize Docker disk usage' and enumerates the object types covered. It clearly distinguishes from system_info (config/counts vs sizes) and ties to pruning tools, so an agent can tell it apart from siblings without ambiguity.

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 says when to use this tool: 'Use it to find what to reclaim before image_prune / container_prune / volume_prune / buildx_prune' and gives the alternative for daemon config: 'use system_info for daemon config and counts rather than sizes.' This is unambiguous routing guidance.

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