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

Beyond the annotations (readOnly, idempotent, non-destructive, closed-world), the description discloses substantial behavioral context: authority scope is not a universal private-employer rule, specific fuel-conservation entries apply to government offices only, the schedule was cancelled April 8, and unlisted notices are not inferred. This is exactly the kind of scope-boundary disclosure that annotations cannot carry.

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?

Uses labeled sections (Inputs, Outputs, Formula, REST fallback, Docs) which aids scanning, but the raw formula line 'working_days += status.is_working_day' and the REST fallback URL are largely redundant for an MCP invocation, and the scope paragraph is dense and hard to parse.

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 the return fields need not be restated, yet the description re-lists output keys—mild waste but not harmful. The scope, exclusions, inputs, and an example are all covered, making it adequately complete for a 4-parameter counter.

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 already 100%, so the baseline is 3. The description adds a complete JSON argument example that shows how the optional include_start_date/include_end_date flags combine with the required dates, providing modest extra value beyond the per-field schema descriptions.

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—counts authority-scope working and non-working dates in a range for Sri Lanka—and the 'Counts ... in a range' phrasing implicitly separates it from the single-date check_lk_working_day and the add_lk_working_days siblings, which are named in the tool list.

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?

Explicitly says when to use it ('auditable Sri Lanka working-day count', call directly rather than answering from memory) and provides a 'Do not use this when' clause covering scope exclusions. The exclusion sentence is grammatically mangled and reads as scope caveats rather than sibling alternatives, so it stops short of a clean 5.

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