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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint. The description adds meaningful context: it explains that the tool reveals holes in the corpus, provides limits that clarify the meaning of version dates and source windows, and explicitly states that it never collapses two different answers. This is valuable behavioral context beyond the annotations and does not contradict them.

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 concise, using three sentences to convey purpose, returns, and usage. It front-loads the core purpose ('Corpus scope with its holes stated') and then elaborates. No wasted words.

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?

With no output schema, the description takes on the responsibility of explaining what the tool returns. It lists categories (totals, per-source windows, count of Aktenzeichen, limits) and explains what limits include. This is sufficient for an agent to understand the tool's output, though it could be more specific about the exact structure. For a zero-parameter tool, this is adequate.

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 does not need to explain parameters, and it doesn't. It doesn't add parameter-specific semantics because there are none.

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 purpose: reporting corpus scope with its holes. It names the resource (corpus), the verb (get coverage), and distinguishes the tool by explaining it returns totals, windows, and limits, and that it differentiates 'outside_coverage' from 'not_in_corpus'. This clearly differentiates it from siblings like getNorm or search.

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 trigger: 'Call this once when your answer depends on whether an absence is real.' It also explains the key usage of distinguishing two distinct concepts, which is a clear instruction for when to use this tool over others. It doesn't need to list alternatives since it's a specialized coverage tool.

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