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

Goes well beyond the annotations by disclosing the concrete side effects: an event on Nikita's calendar, a Google Calendar invite email containing the Meet link, and a cancel link in the result. 'Call it once' explains the non-idempotent hint in operational terms, and 'books the call only' clarifies the boundary of the destructive effect.

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?

Three sentences, front-loaded with what the tool does, then the observable outcome, then the usage rule. No filler, and the most decision-relevant constraint (call once, only after agreement) lands last for emphasis.

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?

A 7-parameter mutation tool with no output schema, yet the description covers the write target, the email side effect, and the return content (cancel link). Combined with full schema coverage, an agent has everything needed to call it correctly and to explain the consequences to the user.

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 schema already defines all seven parameters including the optional phone and time_zone. The description adds provenance for `start` (comes from find_call_times) and a confirmation requirement for the contact details, but it does not add field-level meaning beyond that, so the 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 ('Books') plus the exact resource ('a free 30-minute video call with Nikita Marushkov') and ties the input to the sibling tool find_call_times. An agent can distinguish it from find_call_times, get_booking_link, and get_deposit_link 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?

Gives explicit preconditions ('after the user has seen the exact time in their own time zone and their contact details and agreed') and an invocation rule ('Call it once'). It also scopes the tool negatively with 'It books the call only', which tells the agent not to use it for rescheduling or cancelling.

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