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

Annotations already declare a non-read-only, non-destructive, non-idempotent write, so the bar is lower. The description adds genuine behavioral context beyond that: it refuses overlapping bookings, defers to the owner for outside-hours/time-off requests, and states it does not text the client. It stops short of noting auth requirements or whether re-booking duplicates an entry.

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-loads the action and required fields, then appends constraints in short sentences with no filler. The parenthetical 'plus phone so repeat visits link up' is slightly crammed but still earns its place.

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 9-parameter mutation tool with 33% schema coverage and no output schema, the description covers the main fields and the important behavioral edge cases, but leaves walk_in and notes unexplained and says nothing about the result of a successful booking. Adequate but with visible gaps.

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 only 33%, so the description has to carry weight and it does for some fields: 'phone so repeat visits link up' explains client_phone, and the allow_outside_hours gating explains that flag. But it leaves walk_in, notes, and the required-vs-optional distinction unaddressed, so the compensation is partial.

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 ('Book a client in') and the resource with its key fields (service, date, time, client name/phone), so the agent knows exactly what the tool creates. It does not explicitly differentiate itself from nearby siblings like book_with_pro or find_open_times, which keeps it short of a 5.

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?

Provides real conditional guidance: only set allow_outside_hours after the owner confirms, and it explains that the tool asks first outside working hours. It gives clear context for use but never names an alternative sibling (e.g. book_with_pro, find_open_times) or when NOT to use this tool.

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