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

Goes well beyond the annotations (readOnlyHint=false, destructiveHint=false, openWorldHint=false): it discloses the public, merchant-visible effect of activation, the mandatory confirm gate and that nothing changes without it, idempotent behavior for already-active plans ('returned unchanged'), and a named failure mode SHOPIFY_BILLING_NOT_READY with remediation detail. This is the exact behavioral context an agent needs before a consequential state change.

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?

Front-loaded with the effect of the call, then the confirm gate, then refusal conditions, then return shape — a sensible order with no filler sentences. It is a dense run-on paragraph with mild redundancy ('on the app's pricing page and merchants can subscribe to it, and pay for it if it is paid') that could be tightened.

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?

There is no output schema, and the description compensates by stating the return shape ('same shape as one plans_list entry'). Prerequisites (confirm, app_id, plan_id source), refusal cases, and idempotency are all covered, leaving nothing material an agent needs in order to call 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 coverage is 100%, so app_id, plan_id, and confirm are already documented, and the description largely restates those origins ('plan_id is the uuid or handle from plans_list', 'Takes the app_id returned by apps_list'). The one parameter not addressed at all is organization_id, so no meaning is added beyond the schema baseline.

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 ('Puts a draft Plan Builder plan live') and immediately names the observable consequence: it appears on the pricing page and merchants can subscribe and pay. That is distinguishable at a glance from plan_create, plan_update, or plan_deactivate without opening any schema.

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 explicit when-to-use guidance ('Only pass confirm: true once the developer you act for has decided to offer this plan to merchants') and when-not conditions: refused for an older plan version (activate the current one) and for paid plans while billing is not ready. It stops short of naming plan_deactivate/plan_update as the alternative paths, so it is clear but not fully routed.

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