list_sessions

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

Annotations already declare readOnlyHint=true, so the safety profile is covered; the description adds substantial behaviour: that pending and finished managed sessions have their status deliberately not read, the tri-state meaning of due (true/false/null=unknown), that finished TODOs appear only with includeArchived, and the exact status vocabulary including activeFlags. This goes well beyond the annotation, though propagation/latency behaviour of status is unstated.

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?

Purpose and default scope are front-loaded in the first clause, and every subsequent clause carries new semantics (statuses, TODO tri-state, handoff head). It is a dense single paragraph that runs together return shape, semantics, and permission notes, so it is efficient but slightly hard to scan.

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 carries the burden of describing returns, and it does cover status values, activeFlags, the todos array with due, and handoff — enough to interpret the response. It still omits what a session item actually contains (ids, names, timestamps), so an agent can't fully predict the payload shape.

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 coverage is only 50% (cwd and includeArchived documented, scope and limit not), so the description must compensate — and it does for the highest-risk parameter by spelling out both scope values and their defaults, plus extending includeArchived's meaning to finished TODOs in managed mode. limit's default/purpose is left entirely to the schema.

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 opening sentence names a specific verb and resource (会話の一覧と状態を返す) and immediately distinguishes the two modes by what each returns, so the agent knows this is a list-plus-status read. It does not name a sibling (e.g. read_session for a single conversation's detail), so the boundary with siblings is left implicit.

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 clearly states when each scope applies: managed for supervisor-tracked conversations plus TODO/handoff, all for this PC's conversations in newest order, and ties cwd to scope=all. It also pre-empts a likely doubt by saying the tool may be called from a non-supervisor session — but no explicit 'use X instead when…' routing to read_session or wait_events.

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