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

Beyond the annotations (which already flag non-read-only, destructive, non-idempotent, open-world), the description adds non-obvious operational facts: a Read/Write API key is required, retrying creates a duplicate record, and configured item webhooks fire on success. Those are the exact side effects and preconditions an agent cannot infer from structured fields.

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?

Six tight clauses, front-loaded with the WRITE marker and the resource, followed by scope, auth, idempotency, side effect, and endpoint. No sentence is filler and the ordering matches the decisions an agent makes before calling.

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 14-parameter mutation with no output schema, the description covers auth, side effects, idempotency, and duplicate avoidance. It does not indicate what is returned (e.g., the new item id) or how follow-up stock setup should be done, which is a modest gap for a creation tool.

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 parameter documentation is already handled and the baseline is 3. The description adds value by confirming the sole required field and, more importantly, by declaring that stock quantities are deliberately absent from this endpoint, preventing an agent from hunting for a quantity parameter that does not exist.

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 opens with an explicit "WRITE: create an inventory item" verb+resource statement and scopes it ("name required", "Stock quantities are not set here"), which separates it cleanly from phppos_get_item, phppos_list_items, and phppos_update_item. An agent knows exactly what this tool does without opening the 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 a concrete pre-call flow ("search with phppos_list_items first") and names the sibling to use, plus a scope exclusion (stock quantities aren't set here). It stops short of stating the when-not case explicitly (e.g., use phppos_update_item to change an existing item) or how to set stock afterwards.

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