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

Annotations already state readOnlyHint=true and idempotentHint=true, so the safety profile is covered. The description adds valuable context: it is a pure calculation tool, it does not query data, and it returns a specific set of outputs (max square feet, stories, envelope dimensions, coverage math). It does not discuss behavior with only the required lot_area supplied, but the annotation coverage lowers the burden.

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 uses clear labeled sections (USE WHEN / RETURNS) and front-loads the core purpose. It is somewhat longer than a minimal description, but every section earns its place by covering triggers, outputs, and scope. The final input-summary sentence is a useful recap rather than 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?

Given 7 parameters, no output schema, and strong annotations, the description does the essential work: it specifies return values, input categories, and confirms no data querying. It could add detail on how optional parameters interact (e.g., what happens if constraints are omitted or conflicting), but the overall context is sufficient for an agent to select and invoke the tool correctly.

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% description coverage for all 7 parameters, so baseline 3 is appropriate. The description only restates the input categories ('lot area, setbacks, FAR, height limit, and coverage') without adding new parameter-specific details, examples, or default behaviors.

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 opens with a specific verb and resource: 'Calculate the maximum buildable area (building envelope) for a lot given zoning constraints.' It clearly distinguishes from siblings by stating it is 'a pure calculation tool, does not query data,' setting it apart from lookup_zoning and analyze_property.

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 an explicit 'USE WHEN' section with concrete user phrases ('how much can I build', 'max square footage') and clarifies this is for modeling existing dimensions/zoning rules. It does not explicitly name alternative tools, but the 'does not query data' contrast gives agents a clear signal about when not to use it.

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