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

With no annotations, the description carries the burden and adds meaningful behavior: 'Cache-served when fresh (24h)' and 'Costs 1 credit on a cache miss.' This goes beyond a simple definition, though it doesn't cover error handling or return details.

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?

Two sentences: the first states the core purpose, the second adds caching and cost details. No filler, information is front-loaded and every word earns its place.

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 single-parameter lookup with no output schema, the description adequately explains what it returns and key behavioral nuances (cache, cost). A slight expansion on what 'full property data' includes would improve completeness, but it is largely sufficient.

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 covers the sole parameter zpid 100% with a clear example, so baseline is 3. The description adds no additional parameter-specific meaning beyond confirming it is the lookup key.

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 states 'Returns full property data for a given Zillow property id' with a specific verb and resource, and the 'by_zpid' suffix clearly distinguishes it from lookup_property_by_address, get_zestimate, and search_listings.

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?

Usage is implied (use when you have a zpid), but there is no explicit guidance on when to prefer this over lookup_property_by_address or other siblings, nor when not to use it. No exclusions or alternatives are mentioned.

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