Set the active Zillow session

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

The description discloses that setting the active session affects default routing for subsequent calls, and that explicit session_id parameters can override. With annotations indicating idempotentHint=true and readOnlyHint=false, the description adds context about the functional impact without contradiction. It could mention if the previous session is unaffected, but it's clear enough.

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 with three sentences, all essential. It front-loads the primary action ('Switch which registered session subsequent tool calls route through by default') and provides necessary context about usage and overriding in subsequent sentences.

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, idempotent tool with one parameter and no output schema, the description covers all necessary information: what it does, how to use it, and its interaction with other tools. It is complete without being verbose.

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 input schema has 100% coverage for the single parameter, which already describes it as 'Session id to make active.' The description adds value by specifying that the session_id must be previously returned by zillow_register_session, which is not in the schema, enhancing understanding.

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 switches the default session for subsequent calls, using the verb 'switch' and specifying the resource 'active session'. It distinguishes itself from sibling tools that are about property queries or other session operations like register.

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 explains when to use the tool: after registering a session, to set a default. It also notes that tools with an explicit session_id parameter override this default, providing context for when the tool is not needed. However, it doesn't explicitly state when not to use it, such as when a session is already active.

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