Register a signed-in Homes session

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

Beyond the annotations (readOnlyHint=false, idempotentHint=true), the description discloses key behaviors: re-registering the same identity updates the existing entry, returning a session_id, supporting mark_active to set active in the same call, and explicitly clarifying the registry is a label only and does not affect which account requests use. This is rich, non-obvious context.

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 dense but every sentence contributes: purpose, idempotent update behavior, return value and option, relationship to actual account routing, and cross-tab sign-in context. It is front-loaded with the core purpose and contains 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 3-parameter tool with no output schema, the description provides everything an agent needs: what the tool does, the return value, the active flag, idempotency, and the crucial caveat that it doesn't switch accounts. It also clarifies the integration boundary with the fetchproxy extension context. No significant missing information.

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 already documents all parameters. The description adds extra meaning by explaining `account_identity` is the key for the registry and that `mark_active` can be set in the same call. It does not mention `auth_expires_at`, but the schema covers it, so this is more than adequate.

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 states a specific action (record or refresh a session registration), the resource (Homes account association with the signed-in browser tab), and the keying field `account_identity`. It also clarifies that registration is a label and does not change which account requests use, distinguishing it from siblings like homes_set_active_session.

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 clearly explains when to use the tool: to record or refresh which Homes.com account a tab is signed into. It provides an explicit exclusion by noting the registry does not change account routing, and advises signing the tab into another account to read a different account. It does not explicitly name the alternative tool `homes_set_active_session`, but the guidance is clear enough.

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