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

Annotations already cover readOnlyHint/idempotent/openWorld, so the safety profile is free. The description adds real behavioral context: the data source (CallChatSyn hours or connected Cal.com calendar) and the meaning of an empty slots list. It does not discuss rate limits or staleness, which keeps it short of a 5.

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 scope, then usage, then data source and return contract. Every sentence carries a distinct piece of information (bounds, trigger, provenance, return shape, empty case) with no padding.

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 1-param read tool with no output schema, the description supplies the return shape ({ slots: [{start,label}], services, locations }), the contract for passing 'start' to book_appointment unchanged, and the empty-result semantics. An agent has everything needed to call and interpret it.

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?

Only one parameter and schema coverage is 100%, including the enum and its default, so the schema does the heavy lifting. The description says labels are localized but never mentions the lang parameter or its accepted values, so it adds nothing new here. Baseline 3 applies.

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 (list open appointment times) and immediately bounds it: up to 5, soonest first, next 7 days, in the business's time zone. This is clearly distinguishable from the sibling book/cancel/answer tools.

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 call it ('before book_appointment and whenever a customer asks when they can come in'), naming the sibling tool as the trigger context. Nothing about the selection decision is left to inference.

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