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

Annotations already establish readOnlyHint=true and openWorldHint=false, so the safety profile is covered; the description adds genuinely new behavior detail by disclosing the 2026 data vintage and that every entry carries its base, legal source and the official page it was read from. It does not restate the annotation claims, though it also does not mention error or empty-result behavior (that lives only in the 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?

The first sentence and the closing sibling reference are well-placed and front-loaded, but the middle is a long catalogue of each country's contribution line items that mostly duplicates what the tool returns. It is informative but padded, and the actionable guidance is split between the first and last sentences.

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 the necessary work of explaining the shape and provenance of the returned contributions and enumerating coverage per country. Combined with the schema's error contract (country_not_available), an agent has enough to call this correctly, though it does not state whether results are cached, versioned beyond 2026, or how the lang choice affects the content.

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 coverage is 100% and both parameters are documented in the schema, including the country codes, default and error case, so the baseline is 3. The description's country-by-country enumeration describes what comes back rather than how to set the parameters, and it never mentions the lang parameter's effect, so it adds little parameter-level meaning beyond the schema.

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 gives a specific verb and resource ('Get the social contributions and payroll levies in a country in 2026') and immediately qualifies the payload with its per-item provenance (base, legal source, official page). It also names the sibling tools (calculate_casnos, calculate_ifu) that cover the adjacent estimation use case, so an agent can separate this lookup tool from them without opening a 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 routes one clear case explicitly: 'For an Algerian estimate use calculate_casnos and calculate_ifu', which tells the agent when a sibling is the better choice. It stops short of stating exclusions for the other covered countries or how it relates to list_countries, so the guidance is clear but partial.

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