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

With no annotations provided, the description carries the full burden of behavioral disclosure. It clearly explains that by default the org cancellation policy applies, how the charge is computed (no-charge/partial/full windows), that a penalty transaction may be registered if autoApply is set, and that applyCancellationPolicy: false waives the charge. It also warns that confirm: true is required. This is extensive and transparent about side effects (money-write).

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?

The description is three sentences long and highly efficient. The first sentence states the core purpose, the second explains the default policy behavior and side effects, and the third gives the override option. Every sentence adds value, with no filler or repetition.

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?

Given the tool has no output schema and no annotations, the description covers the main behavioral context: cancellation policy, charge computation, penalty registration, the override flag, and the confirm requirement. It does not describe the return value or error scenarios, but for a mutation tool with this level of behavioral detail, it is reasonably complete. Missing details like what happens if confirm is false or when the policy doesn't autoApply are implied but not explicit.

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 input schema has 7 parameters with 0% description coverage. The description compensates by explaining the semantics of applyCancellationPolicy (waive charge) and confirm (must be true), which are critical. However, it does not clarify the meaning of reason, cancelledBy, orgSlug, sessionId, or apiKey beyond their names, so the compensation is partial.

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 clearly states the tool's function: 'Cancel an existing session.' It also specifies the resource (session) and the action (cancel). However, it does not explicitly distinguish this from sibling cancel tools like scheduling_cancel or portal_session_cancel, though the mention of org cancellation policy adds some differentiation.

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?

The description provides context about the default behavior (applying cancellation policy) and how to waive it, but it does not explicitly state when to use this tool versus the other cancel-related tools in the sibling list. The usage is somewhat implied by the org-specific policy details, but no exclusions or alternative tool references are given.

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