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

Adds real disclosure beyond the annotations: deprecation status and identical-behavior guarantee for backward compatibility, plus "Only the fields you pass are changed" which pins down partial-update semantics that the idempotentHint alone does not convey. The mutation claim is consistent with readOnlyHint=false and destructiveHint=false, and the rename warning is exactly the kind of lifecycle context agents otherwise miss.

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 most decision-relevant fact — DEPRECATED — before any functional prose, which is the right ordering. Slightly verbose in places (the rename rationale is spread over two sentences, and the 'people work out the real question' aside is color rather than instruction), but nothing is wasted enough to impede scanning.

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 6-parameter mutation with no output schema, the description covers scope, partial-update semantics, and sibling routing, which is the bulk of what an agent needs. The only gap is the absence of any statement about what a successful call returns or whether the matching-email rule can fail the call, which matters given no output schema documents 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?

Schema coverage is 83%, so the baseline is 3; the description earns a bump by unpacking the abstract field names ("what the buyer wants to discuss, what they want out of it, or the background they want read first") into topic, desired_outcome and background. It says nothing extra about order_id or the email-must-match constraint, which the schema already carries.

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?

Names a specific verb+resource ("Change the session type or the brief on an existing booking") and enumerates the concrete fields in plain language. It also explicitly states the deprecation rename to update_order_details and distinguishes itself from reschedule_booking, so an agent can tell the three apart 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 an explicit when (buyer refines their thinking after booking), an explicit when-not ("This does not move the meeting — use reschedule_booking for that"), and an explicit preference between siblings ("Prefer update_order_details"). Both alternatives are named with the condition that selects them.

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