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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive behavior, so the safety profile is well covered. The description adds useful context beyond annotations by specifying per-source/per-zone granularity, the possibility of no error, and that the tool is free to use.

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 three short sentences with no wasted words. It front-loads the core purpose, then adds return-field detail and an actionable usage note, all in an efficient structure.

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 tool with rich safety annotations and no output schema, the description is sufficiently complete: it explains what will be returned, the granularity, and the intended use case. Nothing needed for correct selection or invocation 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 tool has zero parameters, so parameter semantics are naturally simple; the baseline for this case is 4. The description correctly mentions the scope ('per source and zone') without inventing irrelevant parameter details.

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 resource ('ingestion health per source and zone') and details the exact data returned (last successful fetch timestamp and last error, if any). This clearly separates it from the listed siblings, which concern data history, latest values, and zone maps.

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 gives an explicit, concrete use case: 'Use it to explain stale or missing values before drawing conclusions from them.' It provides clear context for when the tool should be consulted, though it does not explicitly state when not to use it or name alternative sibling tools.

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