Set the active Homes session

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

Annotations already declare idempotentHint=true and readOnlyHint=false, so the description's disclosure of being a label-only registry adds context without redundancy. It further explains the broader account-routing behavior through the browser tab/fetchproxy extension, which is not in the annotations and clarifies side effects.

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 description is compact, opens with the core action, and every sentence earns its place: the purpose, the label-only caveat, and the account-routing alternative. No filler or redundant restatement of the tool name.

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, no-output-schema tool, the description fully covers what the tool does, its non-effect on account selection, and the browser tab behavior needed to understand its impact. Agents have all necessary context to call it correctly without ambiguity.

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 baseline is 3. The description adds semantic meaning beyond the schema by requiring the session_id to be 'previously registered' (constraint not in the schema) and explains its role as a current label, which clarifies the parameter's purpose in the workflow.

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 ('Mark') with a clear resource ('previously registered session_id') and states the purpose ('current account label... for your own bookkeeping'). It distinguishes itself from homes_register_session (which registers) and homes_get_session_context (which reads) by emphasizing the 'label only' nature, so an agent can tell them apart.

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 description explicitly states when to use it ('for your own bookkeeping across a conversation'), when not to rely on it ('does not change which Homes.com account requests use'), and gives an alternative action for a different goal ('to read a different account, sign that tab into it'). This provides clear when/when-not and alternative routing.

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