Set the active Redfin session

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

Discloses a genuinely non-obvious behavioral fact that annotations cannot convey: the registry is a label only and does not change which Redfin account requests use, with the real switch being the signed-in browser tab. This prevents a costly misconception about auth state. It is consistent with readOnlyHint=false and idempotentHint=true, and adds context beyond them.

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 tight sentences: purpose first, the label-only caveat second, the account-switching workaround last. Every sentence carries information an agent needs; no filler.

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 single-parameter state setter with no output schema and simple annotations, the description covers purpose, the important no-op caveat about account routing, and the alternative path. Nothing required to call 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?

Schema coverage is 100%, so the baseline is 3, but the description adds meaning by qualifying the session_id as 'previously registered', telling the agent the id must originate from the registration flow. No format or syntax detail beyond that.

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 ('Mark a previously registered session_id as the current account label') and immediately scopes it as bookkeeping-only. An agent can distinguish this from the sibling redfin_register_session, which creates the session this tool merely marks active.

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 a clear condition for use ('previously registered session_id', 'across a conversation') and a corrective path for the adjacent need ('to read a different account, sign that tab into it'). It does not explicitly name redfin_get_session_context or redfin_register_session as alternatives, so it stops short of full when/when-not routing.

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