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

Annotations already declare the mutation profile (readOnlyHint=false, idempotentHint=true, destructiveHint=false), but the description adds real context: default no-cap billing behavior, that requests are refused after the cap until the month resets, and that the cost impact should be confirmed. It stops short of describing the response or whether lowering an existing cap is reversible mid-month.

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?

Every sentence carries load, but the description leads with background on default billing before naming the tool's own action, so the core verb lands in sentence two. Dense and efficient overall, just not maximally front-loaded.

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 two-parameter idempotent mutation with no output schema, the description covers defaults, the effect of the cap, how to remove it, where the baseline comes from, and the human-confirmation requirement. An agent has everything needed to call 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?

Schema coverage is 100%, so both parameters are already documented. The description adds meaning beyond the schema: units=null removes the cap, the cap must start at the plan's included requests, and account_id comes from api_account. Useful, though the minimum:1 vs null distinction is largely in 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 states a specific verb (sets/removes) and resource (the monthly API request cap) and explains both outcomes — cap applied or cap removed when units is null. It also distinguishes itself from api_account, which is where the included-request baseline is read rather than written.

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 states when the tool applies (Starter/Pro, which otherwise bill overage without limit), the trigger for removal (units is null), where to source the starting value (api_account), and adds an explicit prerequisite to confirm the number and cost with a person first. Alternatives and exclusions are covered.

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