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

The description adds meaningful behavioral context beyond the annotations: it states the tool returns plain text, is static content, requires no authentication, has no rate limit, and always ends with a provenance caveat. All of this aligns with the readOnlyHint, idempotentHint, and destructiveHint annotations, with no contradiction.

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 information-dense and front-loaded with the core return value. Every clause earns its place, though the caveat is somewhat long. Still, it is structured effectively and not padded.

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 no-argument, read-only tool, the description is complete: it covers what is returned, the exact content, the provenance caveat, when to use it, the alternative for specific estimates, and operational characteristics like auth and rate limits. Nothing necessary for correct 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, and the description explicitly states 'no arguments,' so there is nothing for the agent to infer about parameter usage. This exceeds the baseline for zero-parameter tools by making the lack of arguments explicit.

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: 'Returns zRev's typical engagement results as plain text' followed by concrete metrics. It also names the sibling alternative (estimate_roi) for a different use case, making the tool's purpose unmistakable.

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?

Explicit usage guidance is provided: 'Use when a user asks what results to expect.' It also gives a clear exclusion rule and alternative: 'For an estimate on a specific company's numbers use estimate_roi instead.'

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