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

With no annotations, the description carries full burden. It discloses fail-closed behavior, the need to check availability_state and warnings, and scope across Chronary and authorized human calendars. Absent are rate limits, permission requirements, or error handling details, but the key safety trait is covered.

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?

Two sentences with zero waste: first sentence establishes purpose and scope, second delivers critical behavioral guidance and alias hint. Every word earns its place, and the structure is front-loaded with the most important usage caution.

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 8 parameters and no output schema, the description covers the critical behavioral point (fail-closed, inspect availability_state and warnings) but leaves out what the full output structure looks like (e.g., slots array, busy blocks when include_busy is true). It is adequate for basic use but incomplete for fully autonomous invocation without output schema.

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%, providing baseline 3. The description adds value by clarifying the alias relationship (start/end and start_time/end_time), deprecation of slot_duration in favor of duration, and the default for duration. This aids correct parameter selection beyond schema text.

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 starts with 'Check when a single agent is free', providing a specific verb and resource. It distinguishes from siblings like find_meeting_time (which checks multiple agents) by limiting scope to a single agent across its calendars.

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?

The description states 'fail-closed' and advises inspecting availability_state and warnings, giving usage context. However, it does not explicitly contrast with alternatives like find_meeting_time for multi-agent scheduling or get_calendar for calendar-level views. Usage timing is implied but not fully guided.

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