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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the bar is lower, but the description adds genuinely useful context: the data vintage ('5-year survey estimates, so they describe a period rather than a census-day headcount') and secondary returns (median age, household count, median household income). It does not discuss rate limits or error behavior, keeping it short of a 5.

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?

Front-loaded with the core purpose in the first clause and tightly ordered (purpose, examples, input format, returns, caveat, alternative). It is on the longer side but each sentence carries distinct information, with only minor redundancy in the repeated place examples.

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?

An output schema exists, so return-value detail is not required, and the description still flags the additional returned metrics and the survey-estimate caveat. For this read-only lookup tool with full schema coverage, nothing an agent needs to call it correctly is missing.

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 'place' and 'year' including examples. The description reinforces the plain-English place format and notes the default year is 2022, but adds little syntax or meaning beyond what the schema provides, so 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?

States a specific verb and resource ('HOW MANY PEOPLE LIVE... the population of a county, city, town, ZIP code or state') and names the sibling it is not for ('For what homes cost or rent there, use census_acs'). An agent can distinguish it from census_acs without opening either schema.

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?

Gives concrete query examples ('population of Travis County Texas', 'Ohio population'), explicit input-format rules ('no FIPS codes and no variable codes needed'), and a clear when-not/alternative condition routing housing-cost questions to census_acs.

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