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

The annotations already signal read-only, idempotent, and non-destructive behavior. The description adds valuable detail beyond those hints: 'does not make payments, change accounts, fetch external data, or retain tool inputs,' and it discloses the planning-assumption caveat about issuer reporting dates. No contradiction with annotations.

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 three dense, front-loaded sentences with no filler; the trigger conditions appear first and the caveats are compactly grouped. The final negative list is slightly long but each item serves the transparency goal.

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?

Given the rich schema, strong annotations, and an output schema, the description sufficiently covers invocation triggers, data scope, assumptions, and side-effect limitations. It doesn't explain the priority calculation, but that is reasonable to leave to the output schema and the tool's behavior.

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 covers 100% of parameters with highly detailed descriptions, including defaults, units, and edge cases. The tool description only adds thematic hints like 'which card, how much, and by which date,' which doesn't materially extend the schema's already comprehensive parameter documentation.

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') and resource ('the single highest-priority action') and enumerates the exact user questions it answers ('what to pay first, what to do next, or how to lower utilization'). It distinguishes itself from siblings like simulate_paydown or get_credit_plan by emphasizing 'single' action rather than a plan or timeline.

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?

It explicitly states when to use the tool with three concrete trigger phrases. However, it doesn't name alternatives or state when not to use it, so it stops short of full routing guidance.

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