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

Annotations already declare non-read-only, non-destructive, closed-world behavior, and the description adds important semantics: repeated calls resume the same session rather than resetting progress, and it enumerates the returned session contract. This is exactly the kind of stateful behavior an agent needs beyond 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?

Three sentences, front-loaded with the usage condition, then behavior, then idempotency and return contract. 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?

With full schema coverage, annotations covering safety, and an explicit description of the return contract, the definition is complete enough to call correctly. No output schema is present, but the description compensates by naming returned fields.

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 schema already documents all five parameters including enums and bounds. The description adds no parameter-level detail beyond the general resume concept, so 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 names a specific action (open/resume) and resource (journey), and explicitly covers both starting and continuing. It adds scope detail ('never resets progress') that helps distinguish it from restart_journey.

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 gives a clear triggering condition ('when the user chooses a journey to start or continue') and mentions resume via get_resume_link only in the schema. It does not explicitly name sibling alternatives such as find_journey, browse_journeys, or restart_journey, so it stops short of full when/when-not guidance.

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