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

With no annotations, the description carries the full behavioral burden and does well: it discloses live/real-time behavior, return value, cost/auth implications ('Free, no token'), and the expected call pattern. It could mention side effects or session limits, but the key traits are transparent.

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 short sentences, front-loaded with the core purpose, then return value, then usage pattern. Every sentence earns its place; the style is efficient without being sparse.

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?

The description states the return value (session_id) and the call sequence (session_step/session_end), which is essential since there is no output schema. It doesn't explicitly say the returned session_id must be passed to the siblings, but that is strongly implied. Minor gaps around error behavior or session lifecycle edge cases prevent a 5.

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 single optional agent_id parameter is already fully documented. The description adds no parameter-specific meaning, which is acceptable under the high-coverage baseline.

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 action ('Open a LIVE mid-run session') on a clear resource (Snapback session) with a distinct purpose: real-time warnings on loop/token/cost/context. Also differentiates from siblings by describing the session lifecycle with session_step and session_end.

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?

Clearly says when to use it: mid-run, for live guardian-mode monitoring. Also gives lifecycle usage ('Call session_step as you run, session_end when done'). It does not explicitly name alternatives or exclusions, but the context is strong enough for an agent to select it appropriately.

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