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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely useful behavior beyond that: the unavailable state means 'no referral data imported, which is not zero', preventing a false-zero interpretation. No rate-limit or freshness detail, but the empty-vs-zero distinction is a meaningful addition.

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 what the tool returns, then sibling disambiguation, then the edge case in three tight sentences with no filler. Dense but every clause carries routing or interpretive value; slightly compact phrasing ('for a range') is the only minor friction.

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 no output schema, the description steps up by enumerating the return fields (sessions, share, key events, top landing pages) and explains the unavailable-state behavior. Combined with the GA4 data-source note, an agent has what it needs to call and interpret the result; only pagination/format specifics are absent.

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%, with range enum values and start/end date semantics already documented in the schema. The description only adds 'for a range', which is implied by the schema, so it does not meaningfully extend parameter meaning beyond the baseline for full coverage.

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 resource (visits from AI assistants, sourced from GA4) and enumerates the returned measures: sessions, share of all traffic, key events, top landing pages. It also differentiates from the nearest sibling by noting read_crawl_logs covers crawler requests, so an agent can route correctly without opening a 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?

Explicitly names the alternative read_crawl_logs and the condition that selects it ('people clicking through' vs 'crawler requests'), and points to read_integration_status when data is unavailable. This covers both the sibling-disambiguation and the failure-mode path.

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