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

Annotations already declare idempotentHint=true, readOnlyHint=false, and destructiveHint=false. The description adds beyond that by clarifying partial-update semantics: 'Only the provided fields are changed.' It also explicitly documents that passing completed: false unchecks the item. There is no contradiction with 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?

The description is two sentences with no filler. The main purpose is front-loaded, and the key behavioral detail about partial updates and unchecking is included concisely. Every sentence 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 tool with six parameters and an output schema, the description covers the essential aspects: what the tool updates, how partial updates behave, and how to uncheck an item. Required parameters and their meanings are clear from the schema. A minor gap is that it does not explicitly state that at least one of title or completed should be provided, but the phrasing 'rename it and/or set its completion state' implies this sufficiently.

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 every parameter is already described in the schema. The description adds some semantic value by mapping title to 'rename' and completed to 'completion state', plus clarifying that unspecified fields remain unchanged. This is helpful but does not drastically exceed what the schema already provides, so a 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 states a specific verb and resource: 'Update a checklist item' with the scope 'rename it and/or set its completion state.' This clearly identifies what the tool does. However, it does not explicitly distinguish itself from the sibling checklist_done, which likely also handles completion state, so it stops short of full sibling differentiation.

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 implies the appropriate use case: updating a checklist item's title or completion status. It also gives concrete guidance on how to uncheck an item ('pass completed: false'). It does not, however, mention when not to use this tool or name alternatives such as checklist_done for simply marking an item complete, so usage is somewhat implied rather than explicit.

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