debug_list_active_sessions

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

No annotations are provided, so the description carries the full behavioral burden. It does convey that this is a read-style listing operation returning active, subscribable sessions, which implies no destructive side effects. But it does not disclose the return format, whether sessions are returned with metadata, any ordering or limits, or pagination behavior. It adds some value but lacks rich behavioral context.

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 definition is efficient, with the core purpose front-loaded before the usage hint. The opening sentence '[Arch Debug] Arch connects to live sessions, traces failures, and inspects execution state' provides domain context but is arguably filler that could be trimmed. Overall it is tight and earns its sentences.

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 zero-parameter listing tool with no output schema, the description covers the essentials: what it lists, where from (server), what property the items have (subscribable), and the primary use case (finding UI-created sessions). It doesn't describe the shape of a returned session, but given no output schema and no params, an agent has enough to invoke it 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 tool takes zero parameters, so the baseline of 4 applies — there is no parameter documentation burden for the description to carry. Schema coverage is trivially 100% with an empty schema. The description correctly implies no inputs are needed to call the tool.

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 uses a specific verb+resource ('List all active sessions from the server') and adds meaningful scope ('that can be subscribed to' and 'created by the UI'). It distinguishes this from sibling session tools like debug_session_history and debug_analyze_session by emphasizing active/subscribable sessions from the UI. It stops short of explicitly naming a sibling it is not, which holds it back from a 5.

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 instruction 'Use this to find sessions created by the UI' gives a concrete usage condition, telling the agent when this tool is the right choice. However, it offers no exclusions and names no alternatives, despite several overlapping session siblings (debug_session, debug_session_history, debug_analyze_session) existing. The context is clear but the routing guidance is partial.

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