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

Annotations cover the safety profile (readOnly=false, destructive=false, non-idempotent), and the description adds real behavioral context beyond them: it runs in the background, returns a replayId immediately, and auto-skips validation failures because MCP has no interactive input. It does not mention that resetAppData wipes device data in prose, nor any auth/rate considerations, so it stops short of 5.

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?

Four tight sentences, front-loaded with the action, then the return value, then the sibling routing, then the edge-case behavior. No sentence is redundant.

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?

No output schema exists, so the description carries the return-value burden and does so ('Returns a replayId immediately'). Combined with async semantics and sibling routing, an agent has everything needed to call and follow up correctly.

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 all six parameters including resetAppData and visualCheckEnabled are already documented in the schema. The description adds no parameter-level detail beyond it, so the 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?

States a specific verb and resource ('Kick off a flow replay') and immediately scopes it as background/async, and explicitly distinguishes it from the sibling flow_recording_replay. An agent can tell exactly what this does without opening the schema.

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?

Names the alternative (flow_recording_replay) and the precise condition that selects this tool ('when you want to monitor live or do other work while the replay runs'), plus routes to flow_replay_status for polling. Explicit when-to-use and when-not guidance.

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