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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, so the safety profile is covered. The description adds genuinely new operational context — no authentication and no cost — and outlines the shape of what comes back, which is valuable given there is no output schema.

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?

A single front-loaded sentence identifying the subject ('Where this server's data comes from') before enumerating the four things returned. Every clause carries information; nothing is filler.

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 parameters and no output schema, the description must carry the return-value burden, and it does — enumerating authority, edition, release cadence, and citation. Nothing an agent needs to decide to call it or to interpret the result 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?

Zero parameters, so the baseline is 4; there is nothing to disambiguate and the description correctly presents this as an argument-free call. No wasted space describing non-existent inputs.

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 precisely what the tool returns: per-dataset authority, edition served (naming TIGER/Line, ACS, ZCTA), release cadence, and a ready-made citation string. That content profile is unmistakable against siblings like zip_lookup or validate_address, which return place data rather than provenance metadata.

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?

Implies the use case clearly via 'a ready-made citation string' and 'how often a new release is taken' — an agent can infer this is for provenance/citation questions. 'Costs nothing and needs no key' signals it is safe to call freely, but no explicit triggering condition or when-not guidance is stated (arguably none exists, since no sibling overlaps).

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