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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds context they do not carry: the access requirement ('available to any authenticated user') and the exact shape of the returned payload (source, filter, measure, groupBy, compiledQuerySql, condition), which matters because there is no output schema. It also discloses a scope limitation (no destination data) rather than letting the agent assume.

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 short paragraphs, front-loaded with the operation, then the parameter behavior, then the routing caveat. No sentence is redundant and the scope warning is placed where it is needed.

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 one-parameter read tool with no output schema, the description covers the access model, both call modes, the returned field set, and the adjacent tools for the destination question. Nothing an agent needs in order to call it correctly, or to avoid misusing it, is missing.

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 description coverage is 100% and the single parameter is already documented as 'Optional rule id (UUID); omit to list every rule'. The description restates the same omit/supply semantics without adding format or validation detail, so the schema is doing the work — 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 and resource ('Fetch the calling tenant's alert rules') and explicitly covers both modes: list-all when ruleId is omitted, single-rule fetch when supplied. It also names the siblings it is not (get_alert_rule_destinations / set_alert_rule_destinations), so an agent can route 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 conditional for the single parameter (omit to list, supply to fetch one) and states the boundary case that would otherwise cause a wrong tool choice — that destinations are not returned here — then names the exact alternatives for reading and writing destinations. This is when/when-not/alternatives in full.

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