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

The annotations already indicate readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so the safety profile is known. The description adds valuable behavioral context by enumerating the exact types of data returned (GA4 properties, web streams, app streams, GSC sites, etc.) and the 'connected and missing' distinction. No contradictions with annotations. It stops short of describing return format details, but the output schema covers that.

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?

The description is compact, with two sentences. The first sentence is a long list but is information-dense and necessary to convey the tool's scope. The second sentence gives crisp usage guidance. There is no fluff or redundancy. It could be slightly improved by breaking the list, but overall it is well-structured and appropriately sized.

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?

Given the read-only annotations and the presence of an output schema, the description covers the essential context: what the tool lists, when to use it, and its discovery purpose. The main gap is parameter semantics, which is captured in dimension 4. The tool is simple (list sources) and the description, combined with schema and annotations, is sufficiently complete for an agent to invoke it correctly in most cases.

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 0%, meaning no parameter descriptions exist in the schema. The tool description does not explain the 'sources' array or 'surfaceId' parameter at all. The enum in the schema gives some hint for 'sources', but 'surfaceId' remains completely unexplained. The usage guidance mentions 'property/site selectors' but does not connect them to the parameters. This is a significant gap for a tool with 2 parameters.

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 clearly states the tool's function: 'Lists connected and missing GA4, Google Analytics properties, property IDs, web streams, app streams, measurement IDs, Firebase app IDs, Google Search Console sites, Bing Webmaster sites, and current analysis surface mappings.' This specific verb+resource distinguishes it from sibling tools like marketing_get_report or marketing_get_funnel, which serve different purposes.

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 description provides a clear usage context: 'Use this before reporting when property/site selectors are unknown.' This tells the agent when to invoke this tool, though it does not explicitly mention alternatives or exclusions. It is more specific than a generic 'use this to get sources' and effectively guides the agent to use this tool as a discovery step before reporting.

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