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

Annotations already declare readOnlyHint=false, destructiveHint=false and openWorldHint=false; the description adds genuinely useful behavior context that annotations cannot: it writes a session log, awards points, and persists the answer, and that this mirrors in-app completion. It does not warn that the operation is non-idempotent, i.e. that repeating the call could double-log a session or double-award points, which is the main behavioral risk here.

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?

A single front-loaded sentence with a colon-delimited list of effects, so the agent sees the core action first. It is slightly dense with three effects plus the app-equivalence comparison, but nothing is redundant 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?

For a two-parameter mutation with no output schema, the description covers the write semantics well, but it omits the return value (e.g. points awarded, whether a session id comes back) and what happens if the journey is already completed. Those gaps matter for a non-idempotent write the agent may retry.

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 the schema already explains both journeyId and the 0-9 feeling scale. The description adds only marginal meaning: that the answer is optional ('if they gave one') and is attached to the journey's check-in question. Baseline 3 is appropriate since the structured field does the heavy lifting.

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 uses a specific verb and resource ('Record that the user finished a Reulay journey') and then enumerates the concrete effects: logs the session, adds points, saves the check-in answer. It is clearly distinct from write-adjacent siblings like share_how_you_feel or complete_today_feed, though it never names an alternative explicitly.

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 by 'record that the user finished a journey' and the app-equivalence framing, which tells the agent this is a completion action. However there is no explicit when-not guidance, no mention of a prerequisite start_journey call in the description text itself, and no differentiation from siblings such as share_how_you_feel for a bare check-in answer.

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