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

Annotations already declare readOnly/idempotent/non-destructive, and the description layers on the behavior that matters: Pro-plan gating with the specific error (payment_required), the analytics:read scope and Admin role requirement, a 30-day default window, and a hard 366-day range cap. These are operational constraints not derivable from annotations or schema.

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?

Four sentences, each carrying distinct information: what it returns, when to use it versus the alternative, range defaults/limits, and access requirements. Front-loaded with the output shape so the agent knows what it gets before reading constraints.

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?

No output schema exists, and the description compensates by naming the returned aggregation (counts by status and type) plus the grouping dimension (per-location). Access, plan, and range constraints are all covered, so an agent has everything needed to call it correctly or predict a failure.

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 per-parameter documentation is already handled, and the baseline would be 3. The description adds range semantics beyond the schema — the 30-day default and the 366-day maximum — which are genuine constraints the schema does not state.

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 and resource ('Per-location appointment summary (counts by status and type) over a date range') and explicitly contrasts itself with the sibling list_appointments. An agent can distinguish this reporting tool from the appointment-listing tools 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 a concrete use case ('how many no-shows last month'), names the alternative tool and when to prefer it ('Use list_appointments for the appointments themselves'), and states both plan gating (Pro only, otherwise payment_required) and required scope (analytics:read, Admin role). Nothing about when to select this tool is left to inference.

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