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

Annotations already declare the mutation/non-idempotent profile, but the description adds real behavioral context beyond them: the item is 'Copied into trips created from this program' (a lasting side effect), and headsetPolicy null clears the policy. That is meaningful disclosure the annotations cannot express.

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?

Dense and front-loaded ('Add a stop/leg to a program'), with the highest-value constraints (at-least-one-of, startTime warning, never invent rules) placed prominently. It is long, but given a nested object and 0% schema coverage most sentences earn their place; a few parenthetical length limits could be trimmed.

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?

An output schema exists, so return values needn't be described, and the description covers the nested headsetPolicy object, enum values, ordering model, and side effects. Nothing an agent needs to invoke this correctly appears missing.

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?

With 0% schema description coverage, the description carries the full burden and does so thoroughly: it documents every body field, the templateId-OR-label 'at least one required' rule (absent from the schema), headsetPolicy null-clearing semantics, the groupThreshold 'applies to groups LARGER than this' meaning, and the sourceUrl-required-when-level=required constraint.

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+resource: 'Add a stop/leg to a program.' The agent immediately knows the operation and the target entity. It does not, however, explicitly distinguish itself from siblings like add_trip_item or add_template_schedule_stop, leaving the program-vs-trip-vs-template distinction to inference.

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?

Provides strong conditional usage guidance: do not pass startTime when the time is unknown because ordering comes from dayNumber + insertion order/reorder_program_items, and only set headsetPolicy level=required when a written rule and its https source exist. It never names an alternative tool or an explicit when-not-to-use-this-tool condition, so it falls short of a 5.

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