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

Annotations already declare readOnly/idempotent/non-destructive, so 'Read-only' is redundant, but the description adds genuinely new behavior: mode precedence when both params are supplied and the exact error conditions (unknown destination, invalid month, neither parameter). It stops short of describing pagination or result limits, which a 5 would cover.

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-loaded with the two-mode structure and heavily information-dense, with each clause earning its place. It is somewhat long and the error-handling sentence could be trimmed, but there is little waste.

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?

Despite an output schema existing, the description fully covers the two modes, precedence rules, error behavior, and routing to sibling tools. Nothing an agent needs to call this correctly 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 coverage is 100%, so the baseline is 3, but the description goes further by explaining what each parameter produces: destination yields best/good/avoid months, closures, crowds and events; month yields up to 40 recommended places with reasons. That output-oriented meaning is not in 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?

States a specific verb+resource (get the best time to visit) and immediately clarifies the two operating modes, which distinguishes it from get_destination and list_events. An agent can identify the tool's job 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?

Explicitly names alternatives and their selecting conditions: 'For festival dates alone use list_events; for a full planning guide use get_destination.' It also resolves the ambiguous case with 'If both are given, destination wins,' leaving nothing to inference.

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