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

Annotations already establish readOnly, idempotent, closed-world, non-destructive behavior, so the description's job is to add context — and it does: the ID is deterministic, works offline, and intentionally collapses sub-address units into one building identity. That unit-collapsing rule is a real behavioral trait an agent could not infer from the annotations, though rate limits or failure behavior for unmatched addresses are not covered.

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, front-loaded with the core definition and followed by the chaining guidance. No filler, no repetition of the title, and the scope constraint precedes the hand-off pointers.

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 four-required-param lookup with no output schema, the definition covers the essential shape of the return value (a deterministic FactLot building ID) and where to take it next. It stops short of stating the ID's format or what happens when the address cannot be resolved, which would fully close the loop.

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%, including the important note that suite/unit/floor and anything after a comma is ignored, so the schema carries parameter meaning. The description restates three of the four inputs but omits state_fips entirely, adding little beyond the schema; baseline 3 applies.

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 names a specific verb and resource — a deterministic FactLot building ID derived from a street address — and enumerates the exact inputs (county FIPS, ZIP, street line). It also scopes the result (every condo unit, suite, and floor at the address collapses to the same building ID), which cleanly separates it from the sibling identifiers id_parcel, id_space, id_entity, and id_document.

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?

It gives clear downstream routing: pass the result to id_space for a suite, or to registry_get to inspect the building's parcels. What is missing is an explicit statement of when to prefer this over id_parcel or id_parse for a given address query, so the agent must infer the entry point rather than being told.

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