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

Annotations already declare read-only, idempotent, non-destructive, open-world behavior, so the safety profile is covered. The description adds genuinely new behavioral context: it discloses coverage limits, that missing summaries are returned as null, and that outside-spending totals are separately labeled — details an agent cannot get from the annotations or 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?

Purpose and scope are front-loaded in the first sentence, followed by return-shape notes and interpretive caveats. The three caution sentences ('balances are not net worth', 'contributions do not establish influence') are slightly verbose but defensible for a sensitive-data tool.

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?

Given an output schema exists, the description need not enumerate return fields, and it nonetheless flags the key ones (reporting periods, sources, coverage limits) plus the null-handling contract. For a single-parameter read tool this covers everything an agent needs to invoke and interpret it correctly.

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?

There is a single parameter with 100% schema description coverage, including the pattern and an example, so the schema already carries the semantics. The description only restates 'for an FEC candidate ID' without adding format or sourcing guidance, which is the baseline 3 case.

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 description opens with a specific verb ('Retrieve') and an enumerated resource list (receipts, spending, cash, debts, linked committees, outside-spending totals) scoped to 2026 federal races and keyed by FEC candidate ID. That is immediately distinguishable from the sibling search_* and get_election_* tools, which locate candidates or return electoral outcomes rather than financial disclosures.

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?

The phrase 'for an FEC candidate ID' implies the prerequisite (an ID already obtained elsewhere), but the description never names the alternative tool for finding one, nor states when this should not be used. Usage is inferable rather than guided.

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