Set the active Homes.com session

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

Annotations declare readOnlyHint=false, idempotentHint=true, destructiveHint=false, and the description supplies the crucial behavioral fact those annotations cannot: the registry is a label only and does not change which Homes.com account requests use, plus how routing actually works via the Bridge extension tab. It does not state what happens if session_id was never registered (error vs silent no-op) or whether the call returns confirmation.

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 sentences, zero filler, front-loaded with the action and then the critical caveat. The negative clarification (does not change account) is placed right after the action statement where it prevents the most likely misinterpretation.

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-param state setter with no output schema, the description covers purpose, scope, prerequisite and the key semantic caveat. Missing only the failure mode for an unregistered/unknown session_id and any confirmation of effect, which are minor for this tool class.

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 schema alone justifies a baseline 3, but the description adds real meaning beyond the schema: the id must refer to a *previously registered* session, a constraint not expressible in the minLength:1 schema. That extra constraint is the main thing an agent needs to avoid passing an arbitrary string.

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 disambiguates what 'active' does NOT mean, which is the primary confusion risk for this tool name. An agent can distinguish this bookkeeping op from the actual account-driving sibling tools without opening the schema.

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 ('for your own bookkeeping across a conversation') and the prerequisite is implied by 'previously registered session_id', pointing at homes_register_session. It states what the tool is not for (read a different account) but never names an alternative tool for that goal, so the routing guidance 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.