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

Beyond annotations (readOnlyHint, destructiveHint), the description adds ordering (newest first), the signed semantics of amountMins, and a critical correlation note that providerCallId won't be accepted by get_call and should be matched on apiCallId. These are useful behavioral details not present in structured fields.

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 a single paragraph that front-loads the purpose, then explains filtering, amountMins, and correlation. It is informative without being verbose, though slightly longer than necessary due to the correlation detail.

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 presence of an output schema (which covers return values) and the read-only annotations, the description covers key behavioral aspects like ordering, signed amounts, and correlation with other tools. It lacks explicit pagination guidance beyond the cursor (already in schema) but is otherwise complete for a read-only listing tool.

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 coverage is only 40%, so the description should compensate. It explains the 'type' filter and mentions cursor validity (though that is already in schema), but does not describe the 'to', 'from', or 'limit' parameters. It adds some meaning but does not fully cover the undocumented parameters.

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 lists the organization's balance history newest first, covering call usage, plan renewals, top-ups, coupons, and admin adjustments. It specifies a distinct resource (balance history) and differentiates from sibling list_calls by focusing on usage/balance rows and mentioning correlation with get_call.

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 gives context that this is for balance history and mentions related tools (get_call, list_calls) and warns about providerCallId incompatibility, which implies when to use this vs. those. However, it does not explicitly say 'use this instead of list_calls when you need usage data', but the distinct purpose is clear enough.

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