nonprofit_fetch_nonprofit_by_ein

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

Description explicitly states 'Read-only. No side effects. Idempotent.' Matches annotations (readOnlyHint, destructiveHint, idempotentHint). Also mentions caching behavior (7-day cache). No contradictions.

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?

Very concise yet comprehensive. Front-loaded with key purpose and behavioral traits. Every sentence adds value, including the feedback mechanism call-to-action.

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 has a single parameter, comprehensive annotations, and presumably an output schema (not shown but mentioned), the description is complete. It even includes a fallback feedback instruction.

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 100% for the single parameter ein. Description adds format examples and emphasizes it's required, which improves usability beyond the schema description.

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 explicitly states the tool fetches IRS 990 filing data for a US nonprofit by EIN. It specifies the return data (name, revenue, expenses, etc.) and distinguishes from the sibling tool nonprofit_search_nonprofits_by_name.

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?

Provides clear guidance: use this when you have the exact EIN, use nonprofit_search_nonprofits_by_name when you only have a name. Also includes EIN format examples.

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