upgrade_subscription

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

Annotations already declare destructiveHint=true and idempotentHint=true, but the description goes well beyond them: it discloses that a saved card is charged and prorated, that owner permission is required, and that 3DS or a decline returns a payment link with no state change. That is exactly the behavioral context an agent needs before a money-moving call, and it does not conflict with the annotations.

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 dense and front-loaded: the money warning and owner restriction come before the flow. Every sentence carries a distinct fact, with no filler or repetition of the schema.

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 7-parameter, monetarily destructive tool with no output schema, the definition covers authorization, cost, the preview/confirm handshake, and failure outcomes. It does not describe what the quote response contains or how workspace_id affects scope, which is a modest remaining gap.

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 0%, so the description must carry the load, and it does explain the roles of confirm, preview_id, and the expected_ guard fields, plus the implicit 'tier must be higher' constraint. It leaves interval and workspace_id unmentioned, so a small gap remains.

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 ('Upgrade to a strictly higher plan') and adds a qualifier ('strictly higher') that separates it from downgrade_subscription, cancel_subscription, and resume_subscription without the agent 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?

It gives an explicit two-step protocol: call without confirm to get a quote and preview_id, then call with confirm=true plus that preview_id and the expected_ fields after the user agrees. It also states the 'Owner only' precondition. Nothing about when to use this versus its siblings is left to inference.

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