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

Annotations already declare readOnly, idempotent, non-destructive and openWorld, so the safety profile is covered. The description adds the minimum-filter requirement and a result cap, but 'Returns up to 100 organizations' glosses over the schema's default of 20 and the adjustable limit, giving only modest extra behavioral context.

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, front-loaded with the operation and its filter set, followed by the precondition and result scope. No filler and nothing redundant.

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 single-purpose read-only search with no output schema and full schema descriptions, the definition covers operation, filter constraint, intent, and result volume. Only minor gaps remain, such as the discrepancy between the stated 100-result cap and the schema default of 20.

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 100%, so the schema already documents zip, city, state, and limit formats and ranges. The description restates the location filters and combines them implicitly with 'and/or' but adds no format or combination guidance beyond what the schema provides, so the baseline 3 applies.

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?

States a specific verb and resource ('Find tax-exempt organizations by location') and enumerates the geographic filter set (city, state, ZIP), which implicitly separates it from the name/EIN siblings. It does not explicitly name nonprofit_search_name or nonprofit_lookup_ein as the alternatives, so it falls short of full sibling differentiation.

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?

'At least one filter is required' gives a concrete precondition for calling the tool, and 'Useful for discovering charities, churches, and foundations in an area' frames the intended scenario. No when-not guidance or explicit alternative routing is provided, so it does not reach 5.

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