Update AlzaSubscription installment plan

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

Annotations already declare destructiveHint=true and readOnlyHint=false; the description adds valuable context by emphasizing the high-impact nature (changes payment schedule of a paid subscription) and the requirement for explicit user confirmation. It also reveals the prerequisite token flow, which goes beyond the structured annotations without contradicting them.

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, each earning its place: purpose and method, impact/confirmation/token prerequisite, and values guidance. Information is front-loaded with the purpose and high-impact warning before details. 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?

Given the presence of an output schema, the description doesn't need to explain return values. It covers the essential preconditions (token from prepare_mutation), the required action object, the optional values, and the high-impact nature. An agent has everything needed to invoke 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 description coverage is 100%, so the baseline is 3. The description adds a small hint that values should be copied verbatim from the form response, but the schema already states 'copied verbatim from the form response' for the values property. No significant additional parameter meaning is provided beyond 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 and resource ('Change the AlzaSubscription installment plan') and names the exact server-provided form ('updateInstallmentAction'), making it easy to distinguish from siblings like subscription_activate or subscription_overview. It also ties to the relevant subscription domain without ambiguity.

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?

Provides clear context: high-impact, requires explicit user confirmation, and requires a one-time token from prepare_mutation. It does not explicitly name alternatives or exclusion conditions (e.g., 'use subscription_activate for activation'), but the context is sufficient for an agent to know when this tool is appropriate.

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