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

With no annotations, the description carries the full burden and does well: it discloses that open times already exclude classes, other bookings, blocked time, and the 12-hour notice window, and it specifies the time format (UTC ISO plus the place's IANA time zone). What it omits is any statement about access requirements or side effects, though the read-only nature is strongly implied by 'See'.

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?

The conditional behavior and the empty-result escape hatch are front-loaded, and most clauses earn their place. The closing pointer to the mentor's public profile 'Book a private session' section is orienting but is the least load-bearing sentence and inflates an otherwise dense description.

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 read-only tool with no output schema, the description fully covers the return shape (places, lengths, prices, payment ways, cancellation policy, open times), the empty-result case, and the next action. Nothing an agent needs in order 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 67%, and the description fills the main gap by explaining the conditional effect of durationMinutes (only then are open start times computed) and that `days` bounds the lookahead window. mentorSlug and the enum values are already documented in the schema, so this is genuinely additive rather than redundant.

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 concrete verb and resource ('See what a mentor offers for private one-to-one sessions') and immediately enumerates the returned facets: lengths, prices, payment methods, cancellation policy, and open start times. An agent can tell this apart from search_mentors or list_mentor_class_packs without opening any 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?

It names explicit branches: omit durationMinutes to get only lengths and prices, supply it to get open start times, and an empty `places` list means the mentor has not opened private sessions, in which case use send_mentor_inquiry. It also routes the booking step to book_private_session, so both the alternative and the follow-on action are stated.

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