Zillow56 MCP Server

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It mentions that the data is 'monthly historical' and describes ZHVI as a 'proprietary metric,' but it doesn't cover critical aspects like rate limits, authentication needs, data freshness, pagination, or error handling. This leaves significant gaps for an AI agent to understand operational constraints.

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 appropriately sized with two sentences that are front-loaded: the first sentence states the core functionality, and the second provides context about ZHVI. There's no wasted text, but it could be slightly more structured by explicitly separating purpose from additional context.

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 tool's moderate complexity (2 parameters, no output schema, no annotations), the description is partially complete. It covers the purpose and high-level data context but lacks behavioral details, usage guidelines, and output information. Without annotations or an output schema, the description should do more to compensate, but it provides a basic foundation.

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 description coverage is 100%, so the schema already documents both parameters ('location' and 'type') with descriptions. The description doesn't add any parameter-specific details beyond what's in the schema, such as explaining valid formats for 'location' (e.g., ZIP code) or clarifying 'type' options. Baseline 3 is appropriate when the schema handles parameter documentation adequately.

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: 'provides monthly historical data for the Zillow Home Value Index (ZHVI) for a specified region.' It specifies the verb ('provides'), resource ('monthly historical data for ZHVI'), and scope ('for a specified region'). However, it doesn't explicitly differentiate from sibling tools like 'zestimate_history_zestimate_history' or 'market_data_rental_market_trends', which might offer related but different data.

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 no guidance on when to use this tool versus alternatives. It doesn't mention sibling tools, prerequisites, or specific contexts for usage. For example, it doesn't clarify if this is for historical trends versus current estimates or how it differs from 'zestimate_history_zestimate_history'.

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