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

Annotations already cover the safety profile (readOnlyHint, openWorldHint), so the bar is lower. The description adds real value beyond that: it discloses coverage gaps ('prefectures not covered yet are listed with their official pages'), provenance (source receipt with URL, fetched_at, sha256), and data boundaries (no candidates/votes).

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?

The purpose is front-loaded well, but the second sentence is a dense run-on enumerating every returned field, which is redundant given an output schema exists. The trailing 'Check the official page first' is ambiguous and does not earn its place as written.

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 an output schema present, return values need not be re-explained (though they are). The description adequately covers scope, provenance, and coverage limitations for a read-only query tool. The one weak spot is the unclear 'Check the official page first' instruction.

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 all five parameters (from, to, type, limit, prefecture) are already fully documented in the schema. The description only restates the two-date framing and does not add syntax or format detail beyond what the schema provides. 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 opening sentence states a specific verb+resource+scope: scheduled elections in a Japanese prefecture between two dates. It clearly scopes to election-level facts and rules out candidate/vote data. It does not, however, explicitly differentiate from the sibling election_changes, leaving some ambiguity about which tool to pick.

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 opening question ('which elections are scheduled... between two dates'), and exclusions ('no candidate data, no vote counts') hint at scope. But there is no explicit when-to-use guidance relative to siblings catalog/election_changes/get_receipt, and 'Check the official page first' is cryptic and does not clarify selection.

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