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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, and the description's 'read-only' merely restates that. It adds the useful framing of a raw, customizable query surface but says nothing about rate limits, field-validation failures, or how the request is assembled against the Insights API. With annotations carrying the safety profile, a 3 is appropriate.

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?

A single front-loaded sentence that states the action and the scope before enumerating the knobs. Nothing is wasted and the fallback rationale is not buried.

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 an 11-parameter passthrough query tool with no output schema, the definition is thin: it doesn't explain how date_range interacts with start_date/end_date, what values breakdowns accepts, or how invalid Insights fields are surfaced. Annotations cover safety, but the operational gaps remain for an agent composing a non-trivial query.

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 73%, so the schema already documents most parameters including date_range defaults and account resolution. The description names four of the eleven parameters (level, fields, breakdowns, time_increment) without adding format or valid-value meaning beyond what the schema says, and leaves breakdowns and limit unexplained in both places.

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 ('Run a custom read-only Insights query') and scopes it as the escape hatch for 'analysis not covered by other tools'. An agent can tell it apart from the fixed-report siblings like meta_performance or meta_breakdown, though those siblings are never named 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?

The phrase 'for analysis not covered by other tools' gives a clear fallback-to-this condition and implies the standard report tools come first. It stops short of naming which sibling to try before falling back, so the agent must infer the ordering from the sibling list.

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