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

Annotations cover the safety profile (destructive, non-read-only, idempotent), but the description adds genuinely useful behavior the annotations cannot convey: shared-trip completion semantics (done only once every traveler ticks it), the fact that checked=false unticks, and that an empty category removes the task from its section. It does not mention error behavior or what happens with concurrent edits, which keeps it below a 5.

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?

Front-loaded with the verb and resource, then proceeds through mutable fields, ID sourcing, and per-field semantics in a logical order with no filler. The closing instruction 'Never show IDs to users' is off-topic for tool invocation (a presentation rule) and slightly dilutes an otherwise tight paragraph.

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 5-parameter mutation tool with no output schema, the description covers the mutation surface, the partial-update contract, ID provenance, and the highest-risk behavioral nuance (shared-trip completion). It lacks only edge-case handling (invalid item_id, text trimming) to be fully self-sufficient.

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 100%, so the baseline is 3, but the description adds meaning beyond the field docs: it explains the cross-user effect of checked on a shared trip and clarifies that an empty category detaches the item from its section rather than merely blanking a label. The 'send only what changes' framing also clarifies that all three optional fields are independently omittable.

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?

States a specific verb (change) and a precisely scoped resource (one task on a trip checklist), then enumerates the three mutable aspects: text, category, done-state. That scope cleanly separates it from checklist_items_add, checklist_items_remove, checklist_items_reorder, and library_list_item_update without opening any schema.

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?

Gives a real prerequisite ('Get checklist_id and item_id from trip_checklists') and a usage rule ('Send only what changes'), which tells the agent this is a partial update rather than a full replace. It stops short of explicit exclusions or naming which sibling to use for adjacent operations (reorder, delete).

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