Register a signed-in Homes session

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

The description adds significant context beyond annotations: it explains idempotent update behavior (re-registering same identity updates instead of duplicate), default session assignment, and mark_active effect. Annotations already indicate idempotentHint=true and readOnlyHint=false, which are consistent. The description could further detail side effects or auth requirements but does not contradict 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?

The description is concise—four sentences, front-loaded with the primary action. Every sentence adds essential information: registration/refresh, idempotency, return value, default behavior, and mark_active option. No redundant or wasted words.

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?

Given the lack of output schema, the description adequately explains the return value (session_id) and key behavioral aspects. It covers registration, refresh, idempotency, and active session behavior. Minor gaps: error conditions, authentication prerequisites, or effects of auth_expires_at are not addressed, but the core functionality is well-covered.

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% with descriptions for all parameters. The description adds extra meaning: it clarifies that re-registering the same account_identity updates the session, and explains the significance of mark_active in making the session active immediately. This enriches parameter understanding beyond the schema's basic descriptions.

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 clearly states the tool registers or refreshes an authenticated Homes session, explicitly distinguishing idempotent behavior (updates rather than duplicates) from potential duplication. It differentiates from sibling session tools by explaining the role of 'mark_active' and default session behavior, making its purpose distinct.

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 provides clear context for when to use the tool (registering or refreshing a session) and hints at related functionality (mark_active to set active). However, it does not explicitly exclude alternatives like 'homes_set_active_session' or mention when not to use this tool, leaving some ambiguity for agents.

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