sensing_start_session

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

With no annotations provided, the description carries full weight. It discloses that the tool returns a project summary and a session id, and notes that session_id generation is server-side. However, it doesn't mention potential side effects (e.g., creating records) or error states, leaving some behavioral gaps.

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 two sentences: the first states purpose and return, the second provides session_id guidance. It is front-loaded, contains no filler, and every sentence 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?

Given 3 parameters, no output schema, and moderate complexity, the description sufficiently explains the tool's role and key behaviors (return of summary and id). It could elaborate on the summary content, but is adequate for an agent to use 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?

The input schema covers all 3 parameters with descriptions (100% coverage). The description adds value by explaining that session_id may be omitted for server generation and that the returned id must be used in sibling calls, which is not in the schema. This extra context improves parameter understanding.

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 purpose: 'Signal the start of a new Claude Code session.' It uses a specific verb ('signal') and resource ('session'), and distinguishes it from siblings like sensing_end_session and sensing_record_turn by specifying it is called once at the beginning.

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 says 'Call this once at the beginning of every session,' providing clear when-to-use guidance. It also explains that session_id can be omitted, and that the returned id should be used with sibling tools. It doesn't explicitly mention when not to use or alternatives, but the context is sufficient.

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