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

Annotations already declare the safe read-only, idempotent, non-destructive profile, so the bar is lower. The description adds genuinely non-structured context: that the call is free, that rows come back newest-first, and how to page forward. It does not mention rate limits or retention windows, but that is a minor gap.

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?

Three short fragments, no filler, and the cost and content are front-loaded. It is telegraphic to the point of omitting the verb, but nothing in it is wasted.

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?

An output schema exists, so return shape need not be described, and the three parameters are fully specified in the schema. Ordering and pagination behavior are covered; only explicit when-to-use guidance is absent, which is minor for an unfiltered listing endpoint.

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?

Schema description coverage is 100%, so kind/limit/cursor are already documented in the schema, including the enum values and the 25/100 default. 'Pass next_cursor as cursor' mostly restates the cursor parameter's own schema description, adding little beyond it; baseline 3 applies.

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?

Names the resource content precisely (credit grants, purchases, usage, expiries) so an agent knows this is the billing ledger listing. The verb is only implied by the tool name, and no sibling is named, but the sibling set (accounts, lists, locations) is far enough away that disambiguation is not needed.

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?

'Free.' signals there is no cost barrier to calling it, which is a mild usage cue, but the description never states when to use this tool versus something else, nor any prerequisites. Usage is only implied by the content listing.

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