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

Annotations already declare readOnlyHint=true and destructiveHint=false, covering the safety profile. The description adds behavioral context: it is conversational (requires asking questions) and provides a disclaimer that it's not an IRS ruling. It also implies the agent must interact with the user and relay the outcome, which goes beyond the annotation's simple read-only hint.

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 two sentences, front-loaded with the core purpose, and includes essential context (SSN/passport rule, conversational flow) without fluff. Every sentence earns its place, and it's easy to scan.

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?

The tool has an output schema (not shown), so return values needn't be explained. However, the description misses the 'applyingReason' parameter and mismatches the number of questions to ask. It gives the agent clear conversational guidance but leaves a parameter unexplained, which could lead to incorrect invocation. For a simple check, this is a notable gap.

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 description coverage is 0%, so the description must explain the parameters. It touches on the two booleans via the SSN and passport conditions, but it doesn't explain the 'applyingReason' parameter at all. It also says 'Ask the two questions' while there are three parameters, creating ambiguity. The description partially compensates for the missing schema coverage but not fully.

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 states the tool's purpose: 'Checks whether the user is likely eligible for an ITIN'. It specifies the resource (ITIN eligibility) and distinguishes itself from other ITIN tools (which handle applications, uploads, etc.) by focusing on eligibility assessment. It also clarifies it's guidance, not an IRS ruling, adding precision.

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 implies usage context by instructing 'Ask the two questions conversationally and relay the answer', indicating this is for interactive eligibility checks. It doesn't explicitly exclude other tools, but among the ITIN siblings, only this one is about eligibility, so differentiation is clear. It could explicitly state when to use this over others, but the context is sufficient.

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