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

The description transparently discloses the destructive, non-incremental nature of the operation: 'This replaces the existing list content.' This goes beyond the annotations, which already mark destructiveHint=true and readOnlyHint=false, and there is no contradiction with those 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. It front-loads the use cases and then delivers the critical replacement caveat and unknown-ID fallback, making it highly scannable for an agent.

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?

The core selection criteria, destructive replacement semantics, and unknown-id workflow are covered. The only gap is that for add/reorder/edit operations, an agent may need to fetch the current items first to preserve existing content, and this isn't explicitly called out—though it is strongly implied by 'replaces the existing list content.'

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 parameters like attachmentId, items, title, and timezone are already explained by the input schema. The description adds useful operational context about replacement but does not provide additional parameter-level details beyond what the schema already gives.

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 ('update') and enumerates the exact user intents it covers: edit, add, remove, reorder, or mark items. It clearly identifies the resource as an 'existing Familia checklist/list attachment,' which distinguishes it from create/delete/list sibling 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?

It explicitly states when to use the tool: when the user asks to modify items in an existing attachment. It also provides a conditional workflow: 'list attachments first if the attachment id is unknown.' However, it does not explicitly name when-not-to-use alternatives such as creating a new attachment.

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