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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds real context beyond that: it operates on the journey's draft if one exists, uses a real contact, and explicitly states 'Nothing is written or sent', reinforcing the non-mutating nature.

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?

Two sentences, zero waste, front-loaded with what the tool produces and ending on the critical non-mutation guarantee. Every clause earns its place.

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 no output schema, the description usefully explains what comes back (a step-by-step path with reasons). It is nearly complete; only minor gaps remain, such as how the draft-vs-live choice interacts with the optional events parameter.

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 journeyId, contactId, and the events enum are already fully documented. The description adds no parameter-level detail (e.g., it never mentions the happen/timeout toggle), so baseline 3 applies.

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 gives a specific verb and resource (simulating one contact's path through a journey) and even describes the output shape (step-by-step with the reason at each decision). It does not, however, name or distinguish itself from closely related siblings like get_journey_run, list_journey_runs, or enrol_in_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?

Usage is implied – you would use this to preview/simulate a contact's journey path – but there is no explicit when-to-use, when-not, or named alternative (e.g., to see a past run, use get_journey_run). The agent must infer the context.

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