Price a Usage change before applying it

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

With no annotations provided, the description carries the full behavioral burden and does so well. It explicitly states 'Read-only -- nothing is written,' discloses that the tool validates whether the change is allowed, and explains what results the caller can expect: immediate charge and, with next_term, recurring cost.

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 sentences carry a complete mental model: what the tool does, its side-effect profile, the intended call flow, and the selection rule for params. Every sentence earns its place and the most important fact, 'nothing is written,' is 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 an 8-parameter tool with no output schema and no annotations, the description is unusually complete. It covers the operation, the return semantics, the call ordering relative to sibling writes, and the parameter selection rule. The schema handles per-parameter details, so nothing essential is missing.

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 the baseline is 3, but the description adds meaningful semantic value beyond the schema: it specifies that exactly one of increment, quantity_current, or is_enabled must be passed, and that it must match the Feature's type. This mutual-exclusivity rule is not encoded in the schema itself.

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 ('Prices'), a clear resource ('an intended Usage change'), and a critical qualifier ('without applying it'). It also distinguishes itself from the write siblings it names, so an agent can tell quote_usage_change from add_feature_consumption, set_feature_current_quantity, and set_feature_enabled without opening schemas.

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 explicitly says when to call it: before the three billable write operations, and to show the quoted amount to the customer for confirmation before the write. It also names the alternatives and frames this tool as the read-only pre-write step, giving clear routing guidance.

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