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

Annotations already declare readOnlyHint=true and destructiveHint=false, lowering the bar, and the description adds meaningful behavior beyond them: the output is a single merged result combining two data sources, and it enumerates the data categories returned. It does not disclose prerequisites (whether GA/GSC must be connected via connect_ga/connect_gsc) or latency/rate-limit behavior, which is the remaining gap.

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?

Two sentences, both load-bearing: the first defines the resource and its merged contents, the second routes the agent to prefer this over the split calls. No filler, and the core purpose is front-loaded.

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?

There is no output schema, so the description usefully enumerates the returned data (clicks, impressions, top queries/pages, issues, sessions, users), which compensates well for the missing schema. It stops short of noting that GSC/GA connections are prerequisites, a real consideration given connect_ga and connect_gsc are siblings.

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%, so both site_id and detail are already documented in the schema, including the concise-vs-detailed trimming of lists to top-25. The description adds nothing about either parameter, so the 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 ('performance digest') plus the exact resources it consolidates: Google Search Console metrics (clicks, impressions, top queries/pages, issues) and Google Analytics metrics (sessions, users). It explicitly names the sibling tools it supersedes (get_gsc_metrics + get_ga_metrics), so an agent can distinguish it from those 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?

'Prefer this over calling get_gsc_metrics + get_ga_metrics separately' gives an explicit alternative and a clear selection condition (you want combined GSC+GA data). It lacks the inverse guidance — when a single-source call is preferable (e.g. GSC-only needs, or needing per-tool freshness/detail) — so it falls short of full when/when-not coverage.

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