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

Annotations already declare idempotent (true), non-destructive (true), and not read-only (false). The description adds the specific REST endpoint and the 'in-progress' condition, which provides useful context beyond the annotations. It does not contradict annotations; 'cancel' aligns with readOnlyHint=false. No mention of error behavior, but idempotency covers redundant 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?

A single sentence that is front-loaded with the action ('Cancel') and efficiently conveys the endpoint and key requirement. No redundant words or filler. Perfectly concise and well-structured.

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 simple one-parameter cancellation tool, the description covers the core behavior, the target stream type, and the required stream id. With an output schema present, return values need not be described. It doesn't expand on what constitutes a 'builder stream' or error cases, but the idempotent annotation and low complexity make this adequate.

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 schema already documents stream_id with 100% coverage, including its origin ('Stream id passed when stream-builder was started'). The description's phrase 'using the stream id' merely restates the schema and adds no new meaning. Baseline 3 is appropriate given full schema coverage.

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 cancels an in-progress builder stream and specifies the exact HTTP endpoint (POST /v1/stop-agentic-stream) and required identifier. It distinguishes from sibling tools like stream-builder (which starts a stream) and stop-user-message-stream (which stops a user message stream) by explicitly naming 'builder stream'.

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 clearly sets the context for use: canceling a builder stream that is currently in progress. It does not explicitly mention alternatives or exclusions (e.g., not for user message streams), but the action and target are unambiguous. The sibling stop-user-message-stream provides implicit differentiation, but explicit guidance would earn a 5.

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