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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, and the description reinforces this with "No network call," which is useful confirmation of the parse-only behavior. It goes further than the annotations by describing the decomposition of the return value, though it says nothing about error behavior for malformed or unsupported lengths.

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?

One dense sentence that front-loads the action and output fields with no filler. The nested parenthetical list of length mappings makes it slightly harder to scan than a two-sentence layout would, but nothing is redundant.

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 carries the burden of explaining the returned components, and combined with the annotations it covers safety and network posture. The only gap is failure modes for invalid GEOIDs, which is minor for a pure parsing utility.

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 baseline is 3, but the description adds real meaning beyond the schema by decoding GEOID length variants (2 state, 5 county, 11 tract, 12 block group, 15 block) and the 1400000US prefix form. That tells the agent which inputs are actually valid, which the max/min length constraints alone do not.

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 pair ("split a census GEOID") and enumerates exactly what the split yields: state and county FIPS, tract code, displayed tract number, block group, block. This is unmistakably distinct from the siblings, which are address/coordinate lookups rather than GEOID parsing.

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 rather than stated: an agent can infer it should call this when it already holds a GEOID and needs its components. There is no explicit when-not guidance and no mention of the sibling tools as alternatives, though the difference is obvious from the verb.

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