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

Annotations only declare readOnlyHint=false and destructiveHint=false, a minimal safety profile. The description adds substantive behavior beyond that: a hard 25-item cap, the Free items-per-trip limit checked once per batch, all-or-nothing semantics for both limit breaches and validation/geocoding failures, and pre-write validation. That tells the agent exactly what happens on partial failure.

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, front-loaded with capability then constraints then the routing rule. Every sentence carries a distinct, decision-relevant fact (limit, atomicity, alternative) with no filler.

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 mutation tool with no output schema, the description covers the important risks: batch cap, tier limit, atomic failure and pre-write validation. It does not state permission/auth requirements or whether the trip must pre-exist, which is a minor residual gap.

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 field-level meaning is already documented and the baseline is 3. The description still adds batch-level semantics not expressible per-parameter: the 25-item ceiling, ordered processing ('in order'), and that the entire array commits or fails as a unit.

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?

Opens with a specific verb+resource and scope: 'Add up to 25 items to a trip in one call', enumerating the supported item types. It explicitly contrasts with the sibling trip_item_add, so an agent can separate the batch and single-item tools without opening either 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 an explicit routing rule: 'Use this instead of repeated trip_item_add calls when adding several items at once — it costs one MCP request instead of one per item.' The when-to-use condition and the named alternative are both stated, with no inference required.

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