create_subscription_plan

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

With no annotations, the description does add real behavioral context the schema lacks: the returned planId, the automatic renewal charge to the stored card, and the requirement that the vendor be live. It does not cover idempotency, whether plans can later be edited/deleted, what happens on duplicate names, or auth/error behavior for a mutation tool.

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 compact sentences: what it makes, who it's for, what it returns and how it's used next, then one billing-behavior note. No filler and the key scoping facts are 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, 7-required mutation with no annotations and no output schema, the description successfully covers the return value (planId) and the auto-renewal consequence, which an agent cannot infer elsewhere. The remaining gap is lifecycle behavior (editing/deleting plans, duplicate-name errors), which is secondary for a create call.

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 50%; name, price, period, and access_token are documented in the schema, and the "$12/month" example usefully ties price to periodUOM. The description adds nothing for vendorId, env, or currency beyond their enums, and doesn't clarify the period/periodUOM interaction or the uniqueness constraint on name.

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?

States a specific verb and resource ("Create a recurring subscription plan") and immediately grounds it with a concrete example ("Pro at $12/month") plus the business use cases it serves. The word "recurring" plus the create_subscription_checkout handoff distinguishes it from the one-time create_checkout sibling.

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?

Gives a clear precondition ("for a live vendor", pointing at the go_live sibling) and states the downstream consumer of the returned planId (create_subscription_checkout), which is strong routing guidance. It stops short of explicit exclusions, e.g. when to use create_checkout vs. this tool for one-off charges.

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