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

Annotations already declare readOnlyHint/non-destructive, and the description adds non-obvious semantics beyond them: empty stored mappings do not mean tracking is disabled, values come back with their origin and may be platform fallbacks, and saving a launched campaign can trigger async pushes/refreshes. Much of the timing/token material is pipeline context rather than this tool's own behavior, which keeps it from a 5.

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 opening paragraph is well front-loaded, but the following ~150 words on lead ingestion timing, ad click URL publication, AD_NAME/CAMPAIGN_NAME token resolution, and asynchronous refreshes are largely tangential to a zero-parameter read of account defaults and duplicate context that belongs to set_campaign_utms/get_campaign_utms. For this tool, most of those sentences do not earn their place.

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 parameters and no output schema, the description carries the burden of explaining returns and does so: resolved values, their origin, platform-default fallback, and the meaning of empty mappings. An agent has enough to call it and interpret 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?

The tool takes zero parameters, so the baseline is 4; there is nothing parameter-related the description needs to compensate for, and it correctly describes the returned shape (values plus origin) instead.

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 and resource ('Read the account's resolved UTM defaults by channel') and clarifies the scope of resolution, including platform defaults when no account-specific value exists. That distinguishes it clearly from get_campaign_utms (campaign-level saved mapping) and set_campaign_utms (mutation) among the siblings.

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?

Gives real usage context: it is read-only ('Does not modify defaults') and points the agent to get_campaign_utms to verify saved mappings, with the caveat that live ad click URLs and lead ingestion timing must be verified separately. It never states an explicit when-not condition, so it falls short of a 5.

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