Switch which registered OneHome session is active

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

Beyond the annotations (destructiveHint=true, idempotentHint=true), the description discloses the operational semantics of 'active' — the active session answers all non-`~MLS` requests and any `~MLS` request matching its own MLS, while ambiguous `~MLS` ids error until selection. This routing behavior is exactly the kind of context annotations cannot convey. No contradiction with annotations.

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, each earning its place: purpose, when-to-use with examples, and behavioral consequences. The main verb is front-loaded. It is slightly longer than strictly necessary, but the density of routing semantics justifies the length.

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-switching tool, the description covers the prerequisite (session must already be registered), the failure modes it addresses, where to obtain the session_id, and the post-condition routing rules. It omits the success response format, but with no output schema and low complexity, this is a minor gap.

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 description coverage is 100%, so the schema already documents that session_id comes from `onehome_set_auth` responses or `onehome_get_session_context` listings. The description restates nearly the same provenance information, adding no new syntax, format, or lifecycle detail. Baseline 3 is appropriate since the schema carries the load.

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 pair ('Force a specific registered session to be the active one') and then differentiates itself from siblings by explaining the routing mechanism that makes it distinct from onehome_set_auth (which registers) and onehome_get_session_context (which inspects). An agent can tell exactly what state change this tool performs.

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 gives explicit trigger conditions ('Useful when MLS-suffix routing picks the wrong session') with three concrete examples: two shares in the same MLS, free-text search across MLSes, and a listing without a `~MLS` suffix. It also describes the error case this tool resolves. It does not explicitly state when not to use it or name a direct alternative, so it stops just short of a 5.

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