Set the active Homes session

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

The description explains the side effect: changing default routing for subsequent calls. Annotations indicate idempotent and not read-only, which aligns. It adds context beyond annotations by explaining the override behavior.

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 two sentences, front-loaded with the action, and every sentence adds value. No unnecessary 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?

For a simple tool with one parameter and no output schema, the description is complete. It explains the effect, prerequisite, and interaction with other tools. No gaps.

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?

The schema describes the parameter as 'Session id to make active.' The description adds meaning by specifying it must be 'previously returned by homes_register_session', which is not in the schema. Since schema coverage is 100%, the description provides valuable extra context.

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's purpose: 'Switch which registered session subsequent tool calls route through by default.' It uses a specific verb 'Switch' and resource 'registered session', and distinguishes from siblings by referencing 'homes_register_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 provides clear context: pass a session_id from homes_register_session, and notes that explicit session_id parameters override the default. It lacks explicit exclusions but is sufficient for this simple tool.

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