mark_merged

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

Annotations already declare idempotentHint=true, destructiveHint=false, and readOnlyHint=false. The description goes beyond this by specifying the exact idempotency semantics ('idempotent on identical merge_commit; refuses to overwrite a different one'), which is the concrete behavior an agent needs to predict outcomes on repeat calls.

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?

Three tight sentences, front-loaded with the action, then the calling context, then the idempotency edge case. No filler, though the calling-context sentence could be trimmed without loss for a purely mechanical caller.

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 2-required-param mutation with full schema coverage and annotations carrying the safety profile, the description covers what changes, when it is invoked, and how repeat calls behave. No output schema exists, but the state transition is plain enough that return details are not critical.

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 both handoff_id and merge_commit are already documented, and merge_commit's 'free-form — any opaque identifier works' is captured in the schema. The description adds no format or syntax detail beyond what the schema provides, so the baseline of 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+resource+state change: 'Flip a handoff to status=merged and record the merge commit.' This is clearly distinguishable from siblings like complete_handoff, accept_handoff, or create_handoff, which represent different lifecycle transitions.

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 clear usage context: 'Typically called by an integrator script after the bundle containing the handoff's commit_hash lands in main.' This explains the trigger condition well, but never names a sibling alternative or an explicit when-not-to-use case (e.g., vs complete_handoff).

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