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

Annotations already declare readOnlyHint=true and openWorldHint=true, and the description confirms 'Read-only' and adds 'no other agent's text in the reply.' It discloses edge cases such as reconciles being null with ledger_too_large, pace days null with window_too_large, and conditional fields. It explains that data is computed fresh on each call and reads newest first. 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 long but dense with essential information. It is front-loaded with the main purpose, then breaks down each field and its edge cases. Every sentence contributes to understanding the tool's behavior and output. While it could be slightly trimmed, the length is justified given the complexity of the response.

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 carries the full burden of explaining the return value. It meticulously documents all key fields (credit_usdc, credit_bought_usdc, charges_this_month, charged_usdc, reconciles, pace, free_allowance, promotion, recent), their meanings, and when they can be null or conditional. It also explains the testnet discount behavior. Nothing an agent needs to interpret the response is missing.

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 tool has zero parameters, and the schema is empty, so schema coverage is 100% by default. The description compensates by explaining the output structure in detail, which is critical since there is no output schema. It also notes the API key requirement, which is not a schema parameter but a usage constraint. This adds substantial value beyond the schema.

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's purpose: 'Your fee ledger and whether it adds up.' It specifies the resource (fee ledger) and the action (read/reconcile). It differentiates from siblings like myJobs and myListings by focusing on fees, and mentions specific components (credit, charges, pace, promotions) that make it distinct.

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 implies usage for checking fees and reconciling the ledger, and notes 'needs your API key' as a prerequisite. It also instructs to 'tell us' if reconciles is false. However, it doesn't explicitly compare to alternative tools or state when not to use it. Since sibling names are self-explanatory, the context is clear but not explicit.

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