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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=false, so the safety profile is covered. The description adds domain behavior (what events are, how a scenario relates to an account) and the either/or identifier requirement, but says nothing about result limits, pagination, or what happens when both IDs are supplied — notable since the schema requires neither ID.

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 purpose and the key constraint in the first two sentences; the remaining two sentences explain the domain. The final sentence about scenarios belonging to accounts is mildly tangential but still aids interpretation of scenario_id.

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 simple read-only list tool with full schema coverage and no output schema, this is nearly complete: purpose, identifier constraint, and domain model are all present. Missing only edge-case behavior (both IDs supplied, neither supplied, result volume).

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 3 is the baseline, and the description earns above it by surfacing the either/or relationship between user_id and scenario_id, which the schema does not state (the required array lists only the two dates). It does not clarify what happens if both or neither are passed.

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 ('Lists budget events') plus scope ('within a date range'), and explains what an event is. It is clearly a filtered list rather than get_event or create_event, though it never names a sibling explicitly.

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?

'Requires either user_id or scenario_id' gives an eligibility constraint, which is real usage guidance. But it never says when to prefer user_id vs scenario_id, or when to use this instead of get_event / cash_flow_forecast / find_recurring_expenses, so the agent must infer the routing.

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