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

Annotations already provide readOnlyHint=true, openWorldHint=false, destructiveHint=false, so the safety profile is clear. The description adds useful context by listing the scope of coverage, but doesn't disclose additional behavioral traits like whether it returns structured metadata or how gaps are defined. With annotations covering the core behavior, a 3 is appropriate.

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?

A single, front-loaded sentence that lists the key coverage items without waste. Every word earns its place, and the structure is immediately scannable.

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-parameter tool whose purpose is to describe data coverage, the description is complete. It enumerates the essential aspects an agent needs to know before using other tools, and an output schema likely covers the exact return structure. Nothing 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 schema is empty with 100% coverage, so the baseline is 4. The description doesn't need to explain parameters, and it correctly focuses on what the tool returns. No gap here.

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 (describe) and a clear resource (coverage), then enumerates the exact data aspects (symbols, date range, resolution, structures, gates, biases, cost model, gaps). This distinguishes it from siblings like build_report or explain_methodology, which serve different purposes.

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?

While it doesn't explicitly state when to use this tool versus alternatives, the name and description make the use case obvious: to learn what data is available. Given zero parameters and a self-explanatory purpose, explicit exclusions are unnecessary, but a brief mention of 'use this before querying data' would improve it.

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