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

Annotations already declare the safety profile (readOnlyHint=false, destructiveHint=false, idempotentHint=false, openWorldHint=true), and the description adds real behavioral context on top: what a draft does and does not do ('moves no stock or money'), and that line items are variant id plus replenishment quantity. This is exactly the kind of consequence information structured fields cannot express.

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?

Four tightly packed sentences, front-loaded with the write intent and endpoint, then the draft semantics, then scope exclusions, then the line-item shape. No filler and every sentence carries information an agent needs.

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, 3-required write tool with no output schema, the description covers the operation's meaning and side-effect profile well, and annotations cover safety. Minor gaps remain: it does not say whether vendor/warehouse must already exist in Inventory Planner or how currency defaults are handled.

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 57%, and the description only clarifies the 'items' array shape ('a variant id plus the quantity to order'), which the schema already documents. The remaining parameters (vendor, warehouse, currency, reference, notes, expected_date) get no added meaning in the description beyond what their schema descriptions state. Adequate but not compensating for the coverage gap.

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?

Opens with an explicit verb+resource ('create a purchase order with status "draft"') and even names the underlying endpoint (POST /api/v1/purchase-orders). The scope qualifier 'Purchase orders only (no transfers or assembly orders)' separates it from the other PO-related siblings, and 'create' vs 'update_draft_purchase_order' is 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?

Clearly frames the use case: a draft is a planning artifact that is NOT sent to the vendor and NOT saved to connected systems, so an agent knows this is the right call when staging a plan rather than executing a purchase. It also states exclusions (no transfers or assembly orders). It stops short of naming the sibling (e.g., update_draft_purchase_order) as the follow-up path, so it is strong context rather than full routing guidance.

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