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

The annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds genuinely useful behavioral content beyond them: the result set includes not just active links but pending invitations, which affects how an agent should interpret the output before deciding a link exists. It stops short of mentioning permissions or whether any pagination/limit applies.

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 compact sentence with the resource front-loaded and the clarifying parenthetical and 'pending invitations' scope placed immediately after; nothing is wasted. The trade-off is that the sentence is a bare noun phrase, which reads as a label rather than an instruction to act.

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?

The tool is simple (read-only, three optional parameters, no nesting), and the description plus annotations cover when the data matters. However, with no output schema the description should say a bit more about what a link record contains (status, ID, invitation state), since that is what an agent needs to act on the result.

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 each parameter (folder, account, language, with an enum) is fully documented in the schema, including the folder-vs-account relationship. The description adds no meaning about how folder and account interact or what 'language' changes in the output, so 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?

The description names the specific resource — Merchant Center accounts linked to this Google Ads account — and adds the scope detail 'including pending invitations', so an agent knows exactly what the tool returns. It never differentiates itself from the sibling google_ads_link_merchant_center (the mutation counterpart) and uses a noun phrase rather than an explicit verb, which keeps it below a 5.

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 parenthetical 'needed for Shopping and retail Performance Max' implies a use context (prerequisite checks before launching those campaign types) but never states when to call this tool versus alternatives. Most importantly it is silent on the boundary with google_ads_link_merchant_center, leaving the agent to infer that this reads links while that one creates them.

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