join.hf.direct_vs_metrica_by_utm

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

Annotations already declare readOnlyHint and idempotentHint, so the safety profile is covered. The description adds nothing about how the two data sources are aligned, what happens when no UTM match exists, or default resolution — though the output schema absorbs some of that burden.

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 that states the operation and the join key. The 'Human-friendly:' label is wasted space but the rest earns its 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?

An output schema exists, so return values need not be described, and schema coverage is complete. However, for a cross-platform join with 8 optional parameters and zero required ones, the description says nothing about how defaults resolve or which parameter combinations are needed to produce a meaningful join.

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% across all 8 parameters, so the schema fully documents date ranges, account_id resolution, counter/campaign ids, and the utm_campaign override. The description adds no parameter-level meaning beyond invoking the UTMCampaign concept already in 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?

States a specific verb (join) and both resources (Direct daily performance, Metrica daily visits) plus the join key (UTMCampaign). It implicitly distinguishes itself from the sibling join.hf.direct_vs_metrica_by_yclid, though it never names the alternative. The 'Human-friendly:' prefix is filler rather than clarification.

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 phrase 'using a stable UTMCampaign value' hints at the condition for choosing this tool over the yclid variant, but neither the yclid sibling nor any explicit when/when-not guidance is stated. An agent must infer that 'stable' means preferred over yclid matching.

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