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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description earns credit for going beyond them: it discloses that results are ranked by estimated total yearly cost, that the tax credit is already applied, and that it also returns monthly tax credit, CSR/extra-savings eligibility and likely Medicaid eligibility. It does not say what happens when income is omitted or how ranking degrades without it.

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, zero filler, with the core capability and the ranking/subsidy behavior front-loaded. Nothing is repeated from the schema or annotations.

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 10-parameter read tool with no output schema, the description covers enough: what goes in conceptually and what comes back (ranked plans plus credit, CSR and Medicaid determinations). It stops short of describing the shape of an individual plan result, which leaves the agent guessing at return fields.

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 90%, so parameters are already well documented and the baseline is 3. The description adds only thematic framing (household, tax credit) and no formats, defaults, or interaction rules beyond what the schema states — including the notable interaction between annual_income and the credit it advertises.

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 ACA Marketplace plans for a household") plus two distinguishing behaviors: premium tax credit applied and ranking by estimated total yearly cost. It is clear enough to separate from get_plan (single plan) by implication, but it never names the sibling or explicitly rules out the adjacent tools.

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?

Usage is implied by the framing — you supply a household, income and ages and get ranked plans with subsidy math. There is no explicit when-to-use/when-not guidance, no mention of prerequisites (e.g. annual_income required for a meaningful tax credit), and no routing to check_coverage for a pure eligibility question.

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