Update item fields

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

Beyond the annotations (non-read-only, non-destructive, idempotent), the description discloses shallow-merge semantics, null-based field removal, and optimistic concurrency. It does not cover conflict error handling or permission requirements, but the optimistic concurrency mention is a valuable behavioral hint.

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 short sentences with no filler. It front-loads the verb and object, uses a parenthetical for the key removal detail, and ends with a concise concurrency note.

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 an output schema and annotations, the description covers the core behavioral contract well. The only minor gap is the lack of explicit conflict-handling guidance, but the optimistic concurrency mention plus the schema's expected_version description suffice.

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 only 40%, and the description compensates for the 'fields' parameter by explaining shallow merge and null removal. It also hints at expected_version via optimistic concurrency, but leaves 'actor', 'id', and 'command_id' semantics to the schema or inference.

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 action ('Shallow-merge fields into an item') with a clear resource (an item) and defines the semantics of key removal via null. This clearly distinguishes it from sibling tools like data_add_item, data_delete_item, and data_move_item.

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 clearly implies the tool is for updating existing items via shallow merge, and the null-removal note adds important usage detail. It doesn't explicitly state exclusions or alternatives, but the operation is distinct enough within the data_* sibling group.

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