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

With no annotations, the description carries the full burden. It adds valuable behavioral context: the distinction between knowledge-date span and fiscal-period span, and the semantic warning about results outside the archive's knowledge range. It does not explicitly state read-only status, but the coverage-monitoring nature is clear.

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 sentences, front-loaded with the core concept ('honest bounds of the point-in-time primitive'), and uses every sentence to add value: scope, proper usage, and parameter behavior. No redundancy or filler.

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?

Given the tool's simplicity (one optional parameter, no output schema), the description is remarkably complete. It explains what the tool reports, the subtle as_of semantics, and how to get per-company bounds. The lack of a formal output schema is offset by the detailed prose listing of return information.

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?

Schema coverage is 0%, so the description must compensate for the lone 'ticker' parameter. It does so directly: 'Pass a ticker for per-company bounds,' which also implies that omitting it returns aggregate bounds. This is sufficient parameter-level meaning for a simple optional string.

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 clearly defines the tool's purpose: to report coverage bounds for the point-in-time primitive, including version counts, company counts, knowledge-date span, and fiscal-period span. It uses specific language ('honest bounds', 'call it before trusting an as_of') that distinguishes it from data-query tools like tengu_v3_fundamentals_pit.

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 explicit guidance on when to call the tool ('before trusting an as_of earlier than the archive starts') and explains the critical interpretation ('not knowable here', not 'no data'). It does not name alternative tools, but the 'coverage' framing and sibling names make the use case clear.

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