List all registered Zillow sessions

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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the safety profile is covered. The description adds valuable behavioral detail by specifying the empty-sessions edge case: when no sessions are registered, sessions is empty and active_session_id is null. This goes beyond what the annotations state.

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 short, information-dense sentences. The primary return value is front-loaded, and the edge-case behavior is stated in a separate concise clause. There is no redundant or filler language.

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 parameterless, read-only session-context tool, the description covers the key return values and the empty-sessions behavior. It does not describe the structure of each session object, but given the simple scope and read-only annotations, this is a minor omission rather than a blocking 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?

The tool has zero parameters, so there is no parameter documentation burden. The description instead clarifies what the response will contain, which fully compensates for the absence of an output schema. This is appropriate for a parameterless context getter.

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 ('Return') and names the exact resource ('the full set of registered sessions plus the current active_session_id'). It clearly distinguishes this read-only context tool from mutation-oriented siblings like zillow_register_session and zillow_set_active_session by focusing on retrieval rather than modification.

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 implies this is the tool to call when the agent needs to inspect all registered sessions and the current active session ID. It does not explicitly exclude alternatives, but the read-only nature and focus on session state make the intended usage unambiguous compared to its siblings.

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