subscribe

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

The description adds behavioral context beyond the destructiveHint annotation by clarifying that the tool returns a Stripe Checkout URL for payment completion, rather than immediately creating the subscription. It also discloses pricing tiers, overage rates, and the distinction between monthly/annual billing, which helps set expectations for side effects.

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?

The description is well-structured, opening with the primary purpose and return value, then adding pricing details, and finishing with an explicit alternative. It uses dashes and commas to keep information dense but readable, with no redundant or filler content.

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 tool with a single parameter and an existing output schema, the description covers all critical aspects: the subscription creation flow, pricing specifics, the existence of an alternative for management, and enterprise handling. It is sufficiently complete for an agent to decide when and how to invoke this tool.

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?

Although the schema already describes the 'pro' tier with pricing and credits, the description enriches the parameter meaning by detailing the monthly vs annual options and overage rates, providing the agent with a fuller understanding of the financial implications of choosing 'pro'.

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 clearly states 'Subscribe to a Sablier plan (new subscription)' with a specific verb and resource, and explicitly distinguishes itself from manage_subscription by indicating the new-subscription scope. It also mentions the output (Stripe Checkout URL), making the purpose unambiguous.

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 states when to use this tool vs the alternative: 'To manage an existing subscription (upgrade, downgrade, cancel, update payment), use manage_subscription instead.' It also notes that enterprise pricing is custom and directs users to contact the team, providing clear boundaries for usage.

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