List all registered Redfin sessions

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

Annotations already cover readOnly/idempotent/openWorld, and the description adds substantial non-obvious behavior: the registry is label-only and does not change which account requests use, and every call routes through whichever browser tab the extension is signed into. This is exactly the kind of gotcha an agent needs.

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?

Front-loads the purpose, then adds the empty/null edge case and the label-only caveat. Four sentences all carry information, though the browser-tab explanation is slightly wordy for what it conveys.

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 present, the description steps in to document return fields (sessions empty, active_session_id null) and the key semantic caveat about what the registry does not control. Nothing needed to call or interpret it correctly is missing.

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 per the rubric this is a baseline 4. The description correctly presents it as a parameterless list operation with nothing extra to specify.

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 verb and resource: 'List every registered account label plus the current active_session_id'. It also distinguishes itself from the write-oriented siblings (register/set_active_session) by clarifying the registry is 'a label only'. An agent can identify the tool's scope without opening anything else.

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?

Gives clear context that this reads labels and does not affect which account requests use, plus the corrective action ('sign that tab into it'). It effectively routes away from assuming this tool changes account, but never names the sibling tools (e.g. redfin_set_active_session) that actually change state, so the alternative selection is implied rather than explicit.

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