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

Beyond the readOnly/idempotent annotations it discloses error behaviour (isError with invalid_filter plus a 'cleaned address'), zero-result behaviour (a coverage field explaining gaps and what to do instead, no guessed rating), and partial_coverage for recognizable-but-unrated charities. These are non-obvious response traits an agent could not infer from annotations or schema.

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?

Front-loads the core purpose, but the opening sentence is a dense, awkward appositive ('The Did it work? charity list, filtered: the charities https://... shows for cause, evaluator (by), measure...'). Several clauses (live API URL, index.json equivalence, coverage, partial_coverage) could be tightened without losing information.

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?

With no output schema, the description carries the return burden and does much of it: row links to claims file and API record, JSON shape equivalence to index.json, and the coverage/partial_coverage fields. It still leaves the exact top-level response structure (e.g., where count sits, how parameters with counts are shaped) only partially sketched.

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%, so the baseline is 3, but the description adds meaning the schema lacks: filters hide only, never reorder or score, and the combined filter set matches the static index.json for the same filter. It does not add per-parameter format detail, but the added filter semantics justify going above baseline.

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 (the charity list) plus the five filter dimensions (cause, evaluator/by, measure, follow-up, word search) and that results come in the page's own order. The 'hide-only, never re-order/score/rank' clause sharply separates it from ranking/compare siblings like compare_charities and recommend_charity.

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?

Gives an explicit zero-argument recipe ('call with no arguments to get the full list and every allowed value with its count') and states that out-of-range values return invalid_filter with allowed values, which implies discovery-first usage. It doesn't explicitly say when to reach for compare_charities or search_orgs instead, so it stops short of full alternative routing.

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