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

Annotations already declare the operation read-only, idempotent, non-destructive and closed-world, so the safety profile is covered. The description still adds real domain context the annotations cannot: the tax model (30% flat PFU), the point in time it applies (withdrawal), and the primary returned field. It does not explain the underlying gain formula, but that is a modest gap against annotation coverage.

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 tight sentences with the core definition front-loaded and no padding. The trailing 'See list_bundles' line is a slight self-promotional add-on and '{gain_ratio}' is terse, keeping this just short of a 5.

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?

An output schema exists, so return values need not be spelled out, and the description wisely limits itself to naming the headline field. Combined with 100% schema coverage and full annotation coverage, an agent has everything needed to call it correctly; only the calculation mechanics remain implicit.

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 three parameters are already documented in the schema. The description adds no parameter-level detail beyond that baseline and does not clarify how total_gains_eur, portfolio value and withdrawal amount combine. Baseline 3 is appropriate when the schema carries the parameter semantics.

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 names a specific verb (calculate), resource (French flat tax / PFU on crypto capital gains), and even the exact rate (30% PFU) and triggering event (at withdrawal). This is enough to distinguish it from siblings like calculate_crypto_profit_loss and calculate_french_income_tax without opening any schema.

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?

It implies the applicable context ('at withdrawal'), which is a useful trigger condition. However, it never states when to use this over the closely related calculate_crypto_profit_loss, nor does it name any exclusion. The 'See list_bundles' pointer routes to a bundle lister rather than a competing sibling, so usage guidance is only implied.

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