start_session

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

No annotations are provided, so the description carries the full burden. It discloses internal steps (power_on_all, prepare locomotives), edge cases (exhibition mode refusal, power-on failure skipping step 2), and return structure. This is comprehensive behavioral disclosure.

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?

The description is well-structured with a summary first, followed by usage call, steps, limitations, and return format. It is slightly wordy but every sentence adds value. Could be tightened slightly, but overall efficient.

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?

Given no output schema, the description includes the return format. It covers inputs, behavior, edge cases (exhibition mode, failure), and follow-up actions. It is complete for a session start tool.

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?

There are no parameters, so the schema covers everything. The description adds no parameter-specific detail, but since there are zero parameters, a baseline of 4 is appropriate per guidelines.

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 clearly states the tool's purpose: 'Begin a driving session: power on every DCC system, then prepare every already-acquired locomotive.' It uses a specific verb and resource, and the steps differentiate it from siblings like power_on_all or prepare_locomotive.

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?

The description provides explicit usage context: it is the 'one-call opener' with example phrases. It states when not to use it (does not acquire new locomotives) and suggests alternatives ('follow up with prepare_locomotive/acquire_throttle'). It also notes refusal in exhibition mode and failure behavior.

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