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

Annotations already cover safety (readOnlyHint, idempotentHint, non-destructive, closed-world), so the description's added value is the disclosure that results are ordered by popularity and ratings and that each entry carries fee, rating, tax-benefit, and nonresident fields. It adds real behavioral context beyond the annotations, though it says nothing about result size behavior or truncation beyond what the schema's limit documents.

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?

Two sentences, front-loaded with the purpose and result contents followed by the filter surface; no filler. The first sentence is dense but every clause carries 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 usefully enumerates what comes back (fees, both ratings, tax benefit, nonresident eligibility), so an agent can judge relevance. It stops short of describing ordering ties, pagination, or what an empty filter result looks like, but it is adequate for a read-only listing tool.

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 defines every parameter including defaults and examples. The description's filter summary largely restates those fields, adding only a soft semantic link ('minimum rating' for top_rated); 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 ('List state 529 savings plans') and immediately characterizes the result set: ranked by popularity and ratings, with fees, Morningstar/Saving For College ratings, tax benefit, and nonresident eligibility. It does not explicitly differentiate itself from close siblings like get_529_plan (single plan) or compare_529_plans, though the list/filter framing implies it.

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 second sentence enumerates the available filter axes (state, open-to-anyone, max fee, minimum rating), which implies when each is useful, but there is no explicit when-to-use guidance and no routing away from the sibling comparison or single-plan tools.

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