Register a signed-in Zillow session

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

Goes well beyond the annotations (readOnlyHint=false, idempotentHint=true, openWorldHint=false) by disclosing that re-registration is an update rather than a duplicate, that a session_id is returned, and — most valuably — that the registry is a label only and does not change which account requests use. That last point is a real semantic trap an agent would otherwise fall into.

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?

Four sentences, front-loaded with the verb and keyed parameter, and the mark_active and registry-semantics caveats follow in logical order. Slightly dense, but every sentence carries information an agent needs; nothing is padding.

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?

With no output schema, the description correctly notes it returns a session_id. Combined with the idempotency annotation and the explicit registry-vs-actual-account distinction, an agent has everything required to call this correctly, including the surprising limitation that signing the bridge tab in is what actually switches accounts.

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 account_identity, mark_active and auth_expires_at, making 3 the baseline. The description reinforces mark_active's effect ('mark it as the current account in the same call') but adds no syntax, format, or default information the schema lacks.

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?

States a specific verb and resource: recording/refreshing which Zillow account a signed-in session belongs to, keyed by account_identity. It also implicitly separates itself from zillow_set_active_session by noting that mark_active: true accomplishes activation 'in the same call', so an agent can tell the two apart without opening a schema.

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?

Clear operational context: re-registering the same identity updates the existing entry, and mark_active folds activation into this call. It stops short of an explicit when-to-use-this-vs-zillow_set_active_session or zillow_get_session_context statement, but the implied routing is unambiguous.

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