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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, but the description adds substantial extra context: deterministic exact-coverage calculation, Saturday-Sunday baseline convention, 2026 Gazette pinning for Idd holidays, need to refresh future lunar dates, preservation of the Act's Sunday substitution rule, no Saturday-to-Monday inference, the step-by-step formula, and a REST fallback endpoint. This goes well beyond the structured annotations.

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 front-loaded with the main use case and organized into sections for scope, computation, examples, inputs, outputs, formula, REST fallback, and docs. However, it is verbose, includes an output field list despite an output schema being present, has awkward example user requests, and contains redundant caveat phrasing that could be tightened without losing selection guidance.

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?

For a read-only deterministic calculator, the description is highly complete: it covers scope, limitations, data vintage, holiday policy, formula, inputs, example invocation, outputs, REST fallback, and documentation. The output list is redundant because an output schema exists, but no critical context needed to select or invoke the tool is missing.

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%, and the schema already documents both parameters with descriptions and examples. The description restates the inputs and gives a complete JSON example, but adds little semantic meaning beyond what the schema provides, such as the signed offset and start-date exclusion rule. Baseline 3 is appropriate when the schema does the heavy lifting.

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?

States a specific verb and resource: 'Adds or subtracts Kenya authority-scope working days' and scopes it as a 'deterministic Kenya working-day offset'. This clearly distinguishes it from the many country-specific sibling tools, so an agent can identify it as the Kenya add-offset calculator without opening the 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?

Gives explicit when-to-use guidance: 'when you need a deterministic Kenya working-day offset', and says to call it directly instead of answering from memory. It also lists when-not-to-use cases such as private-employer, bank, school, county, sector, diplomatic, or shift-work calendars. It does not name sibling alternatives such as check_ke_working_day or count_ke_working_days, so it falls short of a 5.

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