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

Annotations already indicate read-only, idempotent, and non-destructive behavior. The description adds valuable behavioral context beyond annotations by warning about partial sector coverage and instructing the agent to read `coverage.classified_pct`. No contradiction with annotations exists.

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 description is three tight sentences with no filler. It front-loads the core purpose, then gives the two most important behavioral caveats. Every sentence earns its place.

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?

The description, combined with the annotations and output schema, is largely sufficient for safe invocation. It covers the main use case, the ranked-breakdown behavior, and the coverage caveat. The main missing piece is the role of `household_id`, though the parameter is optional and the output schema covers return values.

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 0%, so the description must compensate. It does add meaning for `value` and `dimension` by tying them to countries or TRBC sectors and by explaining the effect of omitting `value`. However, `household_id` is not explained at all, leaving a gap for a three-parameter tool.

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 clearly states the tool's function: measuring 'how much of the book sits behind a country (ISO-2) or a TRBC sector, with the positions behind it.' It identifies a specific resource, a specific dimension, and the output nature, which distinguishes it from broader siblings like get_portfolio_positions or get_country_brief.

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 description gives clear usage context: it tells the agent when to omit `value` ('for the ranked breakdown') and advises always reading `coverage.classified_pct` because 'sector resolves for only part of the book.' It does not explicitly name alternatives or exclusion conditions, so it falls short of a 5, but the guidance is actionable and specific.

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