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

Annotations already declare the safety profile (destructiveHint=false, idempotentHint=true, openWorldHint=false), so the bar is lower. The description adds genuinely useful behavior beyond that: the result is scoped to exactly one action plus completion instructions, which matters because there is no output schema to convey the return shape. It does not explain the readOnlyHint=false flag on what reads like an advisory lookup, a minor unexplained note.

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 tight sentences with zero waste: the first front-loads what the tool returns, the second front-loads the usage condition. 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?

For a zero-parameter tool with no output schema, the description covers both the trigger and the return content, which is the essential information. It stops short of noting edge cases such as what happens when onboarding is already complete, which would round out the definition.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate and the baseline of 4 applies. The description correctly implies a parameterless call derived from onboarding state, and adds no misleading input expectations.

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 and resource: it returns 'the single most important next action and how to complete it.' The phrase 'does not want the whole checklist' implicitly distinguishes it from onboarding_status and complete_onboarding_step, though it never names those siblings, so the differentiation is inferred rather than explicit.

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 a clear trigger condition: 'Use when the user asks what to do next and does not want the whole checklist.' This covers when to use it and implicitly when to prefer the fuller checklist view, but it does not name the alternative tool the agent should call instead.

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