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

Goes well beyond the annotations by disclosing non-obvious side effects: holidays replace the location's list for that year (empty list clears it, no location means everyone), already-requested leave keeps the days it was counted with, and the call costs $0.001 with failures free. It still says nothing about what happens to settings not passed in, which matters for a zero-required-parameter mutation tool.

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?

Front-loads the core action in four words, then packs defaults, edge cases, the side-effect caveat and pricing into a tight semicolon-delimited block with no filler. The density makes it a single wall of clauses that takes careful reading, which keeps it off 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?

For a five-parameter mutation tool with a nested holidays object, no output schema and no required fields, the description supplies defaults, clearing semantics, the side effect on existing leave, and cost. The one gap is partial-update behavior — whether omitted fields are left untouched or reset — which is exactly the ambiguity a zero-required schema creates.

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 0%, so the description carries the full burden and does it: ISO weekday numbering and the 1–5 default, hours_per_day's default of 8 and its purpose in leave display, leave_year_start as a month with default 1, time_zone as an IANA name with null fallback behavior, and the nested holidays replacement/clearing semantics including the year scoping.

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?

Opens with a specific verb+resource ("Set the work calendar") and then enumerates the exact settings covered, so the agent knows this is the write-side counterpart of the HR settings read. It never names hr_get_settings explicitly, so sibling differentiation must be inferred from the verb rather than stated.

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?

Usage is implied by the 'set/changing' framing and the presence of defaults, but there is no explicit when-to-use statement, no mention of when to prefer hr_get_settings, and no prerequisites (e.g. admin role) called out. The agent can infer intent but is given no routing rules.

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