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

Annotations already cover readOnly, idempotent and non-destructive, so the description's added value is in telling the agent the numbers reconcile with Dashboard > Analytics and that the range is user-selectable via period. It also clarifies that billing actions are outside the tool's reach, which prevents an agent from attempting a mutation.

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 scope is front-loaded in the first clause and each clause carries distinct information (costs, balances, limits, UI parity, read-only boundary). The middle sentence is a long enumeration and could be broken up, but no sentence is filler.

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?

There is no output schema, so the description rightly takes on the job of listing what comes back, and it does so item by item. Combined with the read-only note and the Analytics parity claim, an agent has enough to decide to call it and interpret the result; only the shape of the response (grouping, totals) stays implicit.

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 100% and the single enum parameter is fully documented, including the default and the meaning of billing_period. The description only echoes the notion of a period without adding format or edge-case guidance, so the schema does the real work.

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 names the resource precisely and enumerates the specific data returned: runs, failures and cost by workflow and by agent, remaining tasks and hosted-model wallet, and assistant daily-limit consumption. It is clearly a reporting/read tool, distinguishable by its cost-and-quota scope, though it never names a sibling such as get_plan_limits to draw the boundary explicitly.

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?

Usage is implied rather than stated: call it when you need to know what runs cost or how much quota remains over a period. The description does give a useful exclusion by noting top-ups and plan changes happen on the billing page, but it points to a human page rather than to any alternative tool an agent could call.

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