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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so safety is covered; the description adds ordering ("newest first"), the system_generated marker for Google's own annotations, and the overlap semantics of the date filter. Enumerating returned fields is partly redundant with the existing output schema, which keeps this from a 5.

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?

Purpose is front-loaded, followed by return shape, then usage routing, which is the right order for an agent scanning for a decision. The trailing developer-docs links are marginal, and the Google Analytics Data API link is not even the API this tool calls (Admin API v1alpha), so a small amount of text does not earn its place.

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?

With an output schema, full annotation coverage, and three fully described parameters, the description needs only to add scope, ordering, filtering behavior and routing — and it does all four. An agent has everything required to decide to call this and to interpret the response.

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 property_id formats and the date_range_start formats ("today", "yesterday", "NdaysAgo", "YYYY-MM-DD") are already documented in the schema and repeating them would earn nothing. The description does add one genuine semantic beyond the schema: a date range returns only annotations that overlap it, which is not obvious from parameter names alone. Baseline 3 plus that single addition.

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?

Opens with a specific verb+resource ("List a GA4 property's annotations") and immediately glosses what an annotation is ("the notes GA4 shows on a date or date range in its charts"). That definition cleanly separates it from the sibling write tool draft_ga4_annotation and from the Ads-side get_change_history.

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 trigger phrase ("The first stop for 'what happened on that day?'") and positions it next to get_change_history in Google Ads, which tells the agent which system to query for which account. It stops short of stating a when-not rule, e.g. that creating annotations goes through draft_ga4_annotation, so a 4 rather than a 5.

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