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

Annotations already flag destructiveHint and idempotentHint; the description reinforces this usefully by explaining the upsert semantics ('a reference that already exists UPDATES that order') and that fulfillment/shipping fees apply. It does not disclose what an update overwrites on the existing order (address, items, date), which is the key gap for a destructive write.

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 WRITE marker and the core action, with operational notes stacked after in priority order. The semicolon-delimited column list is somewhat long and partly redundant with the schema, but the rest is dense and earns its place.

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 13-parameter mutation with full schema coverage, no output schema, and rich annotations, the description covers action, side effects, fee implications, test mode, and data-source guidance. The one missing piece an agent would want is the overwrite semantics when an existing reference updates an order.

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 every parameter is already documented in detail. The description adds the CSV column ordering and the point that each item becomes one row, but that largely restates the schema's fields rather than adding new meaning, so the baseline 3 applies.

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 ('send ONE order to the Zenfulfillment warehouse for picking, packing and shipping') and labels it 'WRITE', which immediately separates it from the read/cancel siblings. It also clarifies the create-vs-update behavior via the reference, so an agent knows exactly which operation this performs.

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?

Explicitly routes the agent to zenfulfillment_list_stock for SKUs and gives a precondition ('Check the address with the user first'), plus notes that test mode ships nothing. It stops short of naming when NOT to use it (e.g. cancel_orders for removals) or stating prerequisites like a configured contract, so not quite a 5.

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