Change / upgrade service product

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

The description discloses that the tool has side effects (changing the product) and that by default it will change something unless dry_run=true is set. It also mentions the pro-rata billing impact, which is beyond what annotations provide. Annotations indicate readOnlyHint=false and destructiveHint=false, and the description aligns without contradiction.

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 two sentences: the first states the primary purpose, the second gives a critical usage tip. It is front-loaded and zero-waste, with no unnecessary details.

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 9 parameters and no output schema, the description covers the core behavior and the most important safety workflow (dry_run). It mentions billing implications (pro-rata) and changing products. It does not explain return values, but no output schema exists to require that. It is reasonably complete for an agent to use 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?

The input schema covers most parameters with descriptions (78% coverage). The description highlights the critical 'dry_run' parameter and explains its purpose ('preview the billing impact without changing anything'), adding value. It does not explain other parameters like refund_source or billing_cycle_months, but the schema already provides that context. Thus baseline 3 is appropriate.

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 the tool's function: 'Upgrade or downgrade a contract product to a different product'. It also distinguishes itself from sibling tools like 'update_contract_product_price' by focusing on product change rather than price or other attributes. The mention of pro-rata invoice/credit note adds specificity.

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 provides a clear recommended workflow: 'Set dry_run=true first to preview the billing impact without changing anything.' This gives the agent a concrete usage directive. However, it does not explicitly mention alternatives or when not to use the tool, though sibling tool names like 'cancel_contract_product' and 'activate_contract_product' inherently differentiate usage.

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