Update an item

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

Annotations already indicate this is a write operation that is idempotent and non-destructive, and the description adds meaningful detail beyond that: PATCH semantics, wholesale replacement of array fields, and automatic reading of the current version unless expectedVersion is supplied. These are exactly the behavioral traits an agent needs to invoke this tool safely.

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?

Three sentences, each earning its place: patch semantics, the crucial array-replacement caveat with routing to alternatives, and version behavior. No filler or repetition of schema 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 an update tool with rich parameter descriptions and an output schema, the description covers the important contextual points: partial updates, array overwrite semantics, the alternative for collection membership, and version conflict handling. An agent has everything needed to select and invoke it 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?

Schema description coverage is 100%, so the schema already documents all four parameters well. The description reinforces the patch semantics and array-replacement behavior but does not substantially extend what the schema already says about individual parameters. This meets the baseline for high schema coverage.

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 uses a specific verb (Patch) with a clear resource ('an existing item') and immediately distinguishes itself from creation and collection-membership tools. An agent can tell this updates an item's fields rather than creating, deleting, or changing collection membership.

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 explicitly states the behavior ('Only the fields passed in `fields` change; everything else is left alone') and names the preferred alternatives for collection membership changes, including why (merge instead of overwrite). It also clarifies version-handling behavior, leaving little ambiguity about when to supply expectedVersion.

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