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

Annotations already indicate this is read-only (readOnlyHint=true), and the description adds meaningful behavioral context by specifying what kind of information is returned: billing term category and renewal/expiration timing. This goes beyond merely restating the read-only annotation without being verbose.

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?

A single, well-structured sentence that front-loads the core purpose and then adds the key output detail. Every word earns its place; there is no redundancy or 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?

For a simple one-parameter read-only tool with an output schema, the description covers the essential semantics: what is retrieved and what additional details are included. The annotations handle safety, and the schema handles the parameter and return structure, so nothing critical 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 description coverage is 100%, and the 'id' parameter is already documented as the instance/agent id returned by create_instance or list_instances. The tool description adds no further parameter-level detail, so the baseline of 3 is appropriate.

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 uses a specific verb ('Get') with a precise resource ('billing term') and lists the possible term categories (trial/paid/grace) plus the time-related details (renews/expires). This clearly distinguishes it from sibling tools like get_instance_health and get_payment_options.

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 gives clear context: use this tool when you need an instance's billing term and renewal/expiration timing. It does not explicitly name alternatives or state when not to use it, but the purpose is evident enough for an agent to route to the correct tool.

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