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

Annotations cover the safety profile (readOnly, idempotent, non-destructive, closed-world). The description adds substantive behavioral context on top: that output includes a range, the underlying model, and its caveats, and the explicit hedge "An estimate, not a promise." That framing is not derivable from the annotations.

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?

Three short sentences plus two inline examples, front-loaded with the returned content before the input guidance. No filler, though the opening sentence is a fragment that reads slightly awkwardly.

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 two-parameter, read-only, no-output-schema tool, the description covers both input paths, the return content, and the reliability caveat. An agent has enough to call it correctly; only rival-tool selection guidance 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?

Schema coverage is already 100%, but the description adds meaning the schema lacks: the conditional rule that a filing date applies only to cases in analyst review, plus worked examples for each parameter. That is genuine value beyond the field descriptions.

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 title and description state a specific verb (estimate) and resource (PERM decision date), and the opening clause specifies the returned content (range, model, caveats). It is clearly distinguishable from lookup_case or queue_status by scope, though it never names those siblings explicitly.

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?

"When a pending PERM case is likely to be decided" plus "Pass a case number, or a filing date for a case in analyst review" gives implied conditions for use and the two input paths. However, it never says when to prefer this over queue_status or lookup_case, so alternative-routing guidance is absent.

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