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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior, so the safety profile is covered. The description adds genuinely useful behavioral context beyond that: the 45-minute slot duration, the America/New_York timezone, and the bookable window constraint. It stops short of describing pagination or the shape of the returned slots.

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?

A single tight sentence covering what the tool returns and the two most decision-relevant constraints (timezone, bookable window). Zero filler and front-loaded with the resource.

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 two-optional-parameter read-only availability tool with no output schema, the description supplies the key domain context an agent needs: timezone, slot length, and bookable horizon. Only minor gaps remain, such as whether results are grouped by day or how many slots are returned.

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 both parameters (days, start_date) are fully documented in the schema itself. The description adds no parameter-level detail such as how 'days' interacts with the 21-day maximum, so the baseline 3 is appropriate.

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 names the specific resource (open start times for a free 45-minute on-site walkthrough) and adds distinguishing scope details like timezone and booking window. It clearly reads as a listing/availability tool distinct from the sibling book_walkthrough, though it never explicitly contrasts itself with that sibling.

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: an agent can infer this is the tool to consult before booking, and the bookable window (24 hours out to 21 days) frames when results are valid. However, there is no explicit when-to-use statement or reference to book_walkthrough as the follow-up action, so the guidance remains inferential.

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