Subscribe a customer to an offer (write)

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

With no annotations, the description carries the disclosure burden and does more than a generic 'creates' line: it flags WRITE, explains that the subscription is a copy of the offer, and defines the Draft vs. active distinction via start_now. The 'pass an override' phrase is not represented in the schema, which slightly muddies the behavioral contract, but the core side effects are clearly conveyed.

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?

Four short sentences front-load the WRITE marker and the core action before adding usage context and state semantics. The 'override' sentence is a little vague and refers to a capability not visible in the schema, so the structure is strong but not perfectly clean.

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?

The description covers the key workflow distinction and the Draft/active semantics, which is helpful for a creation tool with no annotations. However, with seven parameters and no output schema, it omits return values, error conditions, and prerequisites beyond 'existing customer', leaving an agent to infer several call-time details.

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 input schema already documents every parameter; the description adds marginal value by explaining that customer_ref refers to an existing customer and that start_now activates the subscription immediately. It does not enrich the semantics of bill_now, metadata, ensure_billable, or buyer_customer_ref, matching the baseline for full schema coverage.

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 opens with the unambiguous verb 'Creates' and identifies the exact resource ('a ProAbono subscription linking an existing customer to an offer'). It also distinguishes itself from the hosted subscription workflow, so an agent can separate this API-based creation from the customer self-service path.

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 explicitly says this is the API path and that a customer choosing a plan themselves should go through the hosted subscription workflow, providing a clear exclusion. It does not, however, spell out when to use this instead of change_subscription or list_subscriptions, leaving some routing to inference.

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