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

Annotations already establish read-only and non-destructive behavior, and the description adds substantial context: the composition of the data (FDIC averages plus observed rates), the presence of staleness status, and explicit behavioral rules (never recommend a provider, decline stock-moving advice). This goes far beyond what annotations state and gives the agent clear operational boundaries.

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?

The description is a single paragraph with four sentences, covering purpose, parameter usage, and behavioral guardrails. It is front-loaded with the core output and avoids redundancy, though it could be slightly tighter by trimming the example term list (e.g., '3, 6, 12, 24, 36, 60') which is not essential.

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?

There is no output schema, but the description compensates by detailing what data will be returned (terms, minimums/conditions, timestamps, sources, staleness status). It also covers edge cases around advice and provider claims. Given the tool's moderate complexity and full schema coverage, the description is sufficiently complete for safe and correct invocation.

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?

The input schema has 100% description coverage, with each parameter already explaining its purpose (e.g., state adds availability note, balance resolves tier APY). The description only reiterates the term_months filtering behavior, which is already in the schema. No new parameter meaning is added, 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?

The description clearly states the tool provides current CD APYs, specifically FDIC national averages plus RateZip-observed institution rates. It distinguishes itself from sibling tools by emphasizing 'CD' and the specific data sources, making it unambiguous what resource is being queried.

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 description gives clear context for when to use the tool (for CD rate lookups) and how to filter by term_months. It does not explicitly name alternatives like get_savings_rates or get_mortgage_rates, so it lacks explicit exclusions, but the focus on CDs and the behavioral guardrails around financial advice imply the intended use case.

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