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

Annotations already declare readOnlyHint/openWorldHint, so safety is covered. The description adds genuine domain behavior beyond that: Reddit requires conversion_pixel_id on every ad group, and the insights output flags ad groups lacking one and identifies weekly-schedule ad groups. That is real operational context an agent could not derive from the schema.

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?

Front-loaded with the core action and field list, then behavior, then a doc link. Slight redundancy: the first sentence already mentions pixel and weekly schedule, which the third sentence re-explains, costing a little space.

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 spelled out, yet the description still summarizes them (currency, ad groups, insights). Combined with the conversion_pixel_id requirement and insights behavior, an agent has enough to call this correctly; only explicit sibling routing is missing.

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 coverage is 100%, so both parameters are fully documented with defaults and sourcing (campaign id, ad account id). The description only echoes the per-campaign filtering idea and adds no syntax or format detail beyond the schema, matching the baseline for a fully documented 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 and resource ('List Reddit ad groups') and enumerates the returned fields (budget, bid, pixel, weekly schedule, targeting summary). The 'optionally per campaign' clause implicitly separates it from get_reddit_campaigns, but no sibling is named explicitly, so differentiation is only partial.

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 implies the common usage ('optionally per campaign') but never states when to use this tool versus get_reddit_campaigns, get_reddit_ads, or update_reddit_ad_group. The parameter descriptions carry the origin hints (from get_reddit_campaigns, from list_reddit_accounts), but that is schema-level, not description-level guidance.

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