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

Annotations already declare read-only, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds genuinely useful non-structured context: the dataset is incomplete and an empty result must not be read as historical absence, which materially changes how an agent reports the result.

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, no filler, and the core capability is front-loaded ahead of the caveat. Every clause carries information.

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 does enough: it characterizes the returned entities and warns about empty results. It could say more about result shape or whether the snapshot includes geometry, but nothing critical is missing for correct invocation.

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 bbox, lang and the negative-year/BC convention. The description only restates the year and optional region at a high level and says nothing about the lang parameter, 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 ('List') plus the exact resource (states, empires and cultures with an OpenHistoricalMap border snapshot) and scopes it by year and optional region. Very clear on its own, but it never names an alternative like find_polity, so the agent must infer sibling routing from the singular-vs-list distinction.

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 by the scope ('in a given year, optionally overlapping a region'), but there is no explicit when-to-use or when-not-to-use guidance relative to find_polity or search_events. The coverage caveat is about interpreting results rather than about choosing this tool.

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