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

The annotations already declare read-only, idempotent, non-destructive, and closed-world behavior. The description adds meaningful context beyond that: output fields, formula behavior, REST fallback, documentation link, and scope exclusions. No annotation contradiction is present.

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 usage conditions and structured into labeled sections, which helps scanning. However, it is overlong and redundantly enumerates output fields and formula details already covered by the output schema, so not 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?

Given the output schema, annotations, and 100% input schema coverage, the description is more than complete. It covers purpose, usage, exclusions, inputs, outputs, fallback endpoint, and documentation, leaving no critical gap for correct invocation.

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 the schema already documents start_date, end_date, and the two include booleans. The description lists the same parameters and gives a complete JSON example but adds no new semantic detail or usage nuance 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 description states a specific verb and resource: counting Mexico working and non-working dates in a range. It also distinguishes scope from discovery and memory-based answers. While it does not name a sibling tool, the operation and country are unambiguous against siblings like add_mx_working_days and check_mx_working_day.

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 gives an explicit 'Use this when' condition and a 'Do not use this when' exclusion involving article 69 weekly rest and out-of-scope calendars. It does not name an alternative MCP tool to use instead, so it falls short of full routing guidance.

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