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

With no annotations, the description carries the full behavioral burden. It does disclose one meaningful trait beyond the schema: the run ends in a terminal state, so no further advancement is possible without a reopen. It says nothing about permissions, irreversibility, what happens to linked work, or failure modes, and the 'terminal' claim is left unqualified even though process_run_reopen exists as a sibling.

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 short sentences with zero filler; the primary action and its terminal semantics are front-loaded, and the disambiguation clause follows. 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?

An output schema exists, so return values need not be described. The description covers the state transition and one alternative, which is close to sufficient for a single-purpose state-mutation tool, though a caller would still be guessing about preconditions (run must be active) and the effect on linked work.

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%, and the schema already explains run_id, reason (kept on the event and audit row), and the agent attribution override, so the baseline of 3 applies. The description adds no parameter-level detail such as format, required run state, or how reason is surfaced downstream.

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 ('End'), resource ('Process run'), and the resulting state ('failed', marked terminal), which separates it from the success-terminal sibling process_run_complete. The differentiation from siblings is partial: it names an alternative as 'cancel', but no sibling is literally named cancel (the closest is agent_run_cancel, which targets agent runs), so the routing hint is slightly ambiguous.

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?

Provides explicit context for choosing this tool ('End an active Process run as failed') and names the condition that selects an alternative ('Use cancel for a run that is dropped'). It does not, however, state the prerequisite that the run must currently be active or contrast with process_run_complete/process_run_reopen by name.

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