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

Annotations already indicate readOnlyHint=false and destructiveHint=false. The description adds transparency by stating that the action replaces assignments and affects only collaboration state, not the revision itself. This helps the agent understand the scope of side effects, which is valuable beyond the annotations.

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?

Two concise sentences, with the key action and object placed first. Every word adds value: the first sentence states the operation, the second clarifies the non-destructive scope. No filler or repetition.

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 only two parameters and no output schema, the description fully captures the purpose, behavior, and scope. It answers the likely questions: what does it change, and what does it not change. No additional context is needed given the simplicity and the rich schema.

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?

The input schema already has 100% description coverage: 'handoverId' and 'principalIds' are clearly explained with patterns and constraints. The description reinforces the replacement semantics but does not add new details about parameters beyond what the schema provides. Baseline 3 is appropriate.

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 the specific verb 'Replace' and clearly identifies the resource: 'the open assignments' with 'supplied collaborator identities.' It also establishes what the tool does NOT do ('not the immutable handover revision'), making its scope unambiguous and distinguishing it from other handover-related tools.

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 conveys the tool's effect and implies its use case: to set or update handover owners. It does not explicitly name alternative tools or exclusion criteria, but the distinction between the mutable collaboration state and the immutable revision provides practical guidance. A clear 'when to use' statement with sibling comparisons would elevate it to a 5.

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