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

The annotations already declare readOnlyHint=true, and the description does not contradict it. It adds meaningful context beyond the annotation by explaining the computation ('asset-weighted z-score of QoQ net interest margin change from FDIC call reports, 20-quarter window, monthly since 1982') and the exact output fields, which enhances transparency.

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 two sentences with no redundancy. It front-loads the core return value and methodology, then lists use cases, then states update frequency. Every sentence contributes essential information, keeping it concise and well-structured.

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 read-only tool with one optional parameter and no output schema, the description covers the key dimensions: what is returned (including field names), temporal scope, update cadence, and when to invoke it. The optional 'days' behavior is fully documented in the schema, so there are no significant gaps.

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 schema description coverage is 100%: the only parameter 'days' has a detailed description including limits and tier requirements. The tool description adds no parameter-level information, but since the schema fully documents the parameter, the baseline score 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 opens with a specific verb and resource: 'Returns a 0-100 bank NIM compression score' followed by precise methodology and output field names. This clearly distinguishes the tool from any sibling, even without naming alternatives, because the subject is unique and the resource is well-defined.

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?

Explicit call triggers are listed: 'Call when the user asks about bank net interest margins, sector margin squeeze, banking profitability, or rate-cycle impact on lenders, or when timing bank-counterparty risk escalation, covenant reviews, or credit-exposure monitoring.' However, there is no 'when not to use' or reference to alternative tools, so it misses the top score.

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