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

The description adds significant behavioral context beyond the readOnlyHint annotation: entries are ordered 'newest first', each entry includes the balance after it, and the semantics of the 'free' flag are explained (amount reflects hypothetical cost, no credits moved). It also notes that filters exist. This fully discloses the tool's behavior without contradicting 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 four sentences, each adding value: the core purpose, filtering capability, a specific use case, and a nuanced output detail (free flag). It is front-loaded with the primary action and avoids fluff. No wasted words.

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 list tool with six optional parameters and no output schema, the description covers purpose, ordering, filtering, and a special field semantics. It doesn't explicitly mention pagination (though page/limit are in the schema) or the return format, but these are standard for list tools. The description is comprehensive enough for an agent to invoke it correctly.

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 provides 100% coverage for all six parameters, so the description doesn't need to explain them. It does mention filtering by 'movement kind, reason or a time window', which maps to parameters, but adds no detail beyond what the schema already provides. Baseline 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 clearly states the verb 'Lists', the resource 'credit ledger', and specifies the contents (grants, spends, reservations, refunds with balance). It also differentiates from get_credit_balance by emphasizing the ledger history. This is precise and distinguishes it from sibling tools.

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 explicit use cases: 'see where credits went' and 'check for a stripe_topup entry after an unconfirmed purchase_credits call'. While it doesn't explicitly name alternatives, it implies the tool is for detailed history rather than a balance snapshot, and it mentions filtering to narrow down. This provides clear context but lacks an explicit 'instead of X' comparison.

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