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

Annotations already mark this as read-only, so the bar is lower; the description adds meaningful behavioral context beyond that: it discloses the index range (0-100), methodology (branch density and deposit growth scaled by bank failure rate), historical depth (quarterly since 1976), and update frequency. It does not go into depth about failure_risk_indicator semantics, but the added context is substantial.

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 compact and well-structured: the first sentence states what it returns, the second gives usage triggers, and the third notes update frequency. Every sentence earns its place and there is no fluff or repetition of schema fields.

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 covers the key return fields, data source, index scale, historical availability, and update cadence. The one optional parameter is fully documented in the schema. It lacks detailed definitions of the output fields or an example, but for a read-only index query tool it provides sufficient context for selection and 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 single parameter (days) is fully described in the schema at 100% coverage, including its optional nature, history-series behavior, maximum 1825 days, and Gold tier requirement. The description itself does not mention the parameter, but since the schema carries the full semantic weight, the baseline of 3 is appropriate.

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 uses a specific verb ('Returns a 0-100 US bank stability and branch coverage index') and clearly identifies the resource and scope. It also lists the output fields (stability_index, branch_density_score, failure_risk_indicator) and cites data sources, making it unmistakable what this tool provides and how it differs from generic adw siblings.

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 explicitly states when to call the tool: 'Call when the user asks about banking system health, bank failures, branch density, deposit growth, or regional banking access, or when timing credit-risk premiums...' This gives clear context for use, though it does not name alternative tools or provide when-not-to-use exclusions, so it stops short of the highest bar.

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