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

Annotations already declare readOnlyHint=true, destructiveHint=false and a closed-world scope, so the safety profile is covered. The description adds the useful details of workspace-wide scope and the optional single-client narrowing, but says nothing about result shape, ordering, or pagination.

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 with the resource and scope stated first and the filter qualifier second; nothing is redundant or padded.

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 a zero-required-parameter read-only list tool with no output schema and full annotation coverage, the description supplies enough to call it correctly. It is only marginally short on what the listing returns.

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% with one parameter, so the schema already documents clientId. The description's 'optionally filtered to one client' confirms the optional semantics but adds no format or behavior detail beyond the schema.

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?

Specific verb 'List' plus the resource 'connected data sources' and concrete examples (Google Ads, GA4, Meta, Search Console) that distinguish it from other list_* siblings like list_clients or list_prompts. It doesn't explicitly name a sibling to route away from, so it stops short of 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 clause 'across your workspace, optionally filtered to one client' implies the filtering context, but there is no explicit when-to-use guidance, prerequisites, or mention of an alternative tool for a different scope.

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