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

With no annotations, the description fully discloses critical behaviors: independent, null-tolerant counts ('reports null, never a silent zero'), cacheability for ~10 minutes, and public accessibility. These traits go beyond the basic 'read-only' implication and are genuinely useful for an agent deciding to call the tool.

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 yet dense. The first sentence defines the tool, the second clarifies scope and distinction, the third gives usage context and examples, and the last addresses edge-case behavior and caching. Every sentence earns its place, and key information is front-loaded.

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-param read-only tool, the description covers the essential contextual ground: what's included (publishers, SSPs, DSPs, etc.), how to use it, and behavioral quirks (null tolerance, cache). The only minor gap is not describing the exact return structure (since no output schema exists), but the descriptive categories are likely sufficient for an agent.

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 baseline is 4. The description adds no parameter syntax (unnecessary), but it does reference the 'scry block' in the output, which indirectly hints at response structure. This is acceptable given the empty input schema.

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 nails the purpose: a 'state of the corpus' readout that spans multiple layers. It uses a specific verb ('get') and resource ('stats') while detailing exactly what is covered, and it explicitly distinguishes from Scry-only sensor stats, effectively differentiating it from potential alternatives.

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?

It provides explicit when-to-use guidance: 'Use it to cite live coverage.' It also offers a clear alternative/exclusion: 'Distinct from the Scry-only sensor stats at api.tunnelmind.ai/v1/stats'. This tells the agent both when to invoke this tool and when not to.

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