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

Annotations already declare read-only, idempotent, closed-world behavior, but the description adds genuinely new traits: output is compiled from the runbook declaration, costs nothing (no generation expense), and 'cannot drift from what the stamper enforces' (deterministic fidelity). It also discloses the audience asymmetry versus emit_runbook_surface, which annotations cannot express. It stops short of describing the concrete return shape, keeping it from a 5.

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 sentences, front-loaded with the core action and contents, then the disambiguation, then the usage trigger and handoff — nothing is redundant. It loses a point for internal jargon ('the frame it reads against', 'what the stamper enforces') that costs an agent a beat of parsing.

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?

With no output schema, the description must characterize the return value, and it does at a useful level (frame, lenses, and questions) plus the instruction to feed it to render_surface. For a single-parameter, annotation-covered read tool this is close to complete; only the exact payload type is left implicit.

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 single parameter is fully documented in the schema (100% coverage) with an enum of the two valid runbooks, so the schema carries the semantics. The description adds no format or selection guidance for runbook_id beyond the notion that it must be a 'stampable runbook' — the documented baseline of 3 for high schema coverage applies.

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 names a specific verb and resource ('Explain a playbook') and immediately scopes it to a human audience via a rendered surface, listing the concrete contents (frame, lenses, questions). It explicitly demarcates itself from emit_runbook_surface and identifies render_surface as the downstream consumer, so an agent can distinguish it from siblings without opening any schema.

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?

It gives an explicit trigger ('Use this when someone asks what a playbook does or how it works'), an explicit negative case ('This is NOT emit_runbook_surface discovery — that returns a contract addressed to YOU'), and a follow-on action ('pass the result to render_surface'). The when/when-not/alternative triad is fully present.

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