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

Annotations already declare readOnly/openWorld/non-destructive, so the bar is lower, and the description still adds real behavioral context: it enumerates returned fields (pixel_id, name, last_fired_at per event, custom events, never_fired) and explains what the 'insights' actually flag (never-fired pixels, mismatched ad group optimization events).

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-loads what the tool returns, then the usage rationale, then the API reference. Efficient and well ordered, with only slight redundancy between the field list and the insights sentence.

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-format detail is not required, and the description already covers purpose, key fields, and the decision context for conversion-optimized campaigns. Adequate for a single-param read tool.

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?

Only one parameter with 100% schema description coverage, including the empty-string fallback to config, so the schema does the heavy lifting. The description adds no parameter-level info, which is the expected baseline when coverage is this high.

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 (get) and resource (Reddit pixels) and immediately scopes the payload: 'when each event (purchase, sign_up, lead, ...) last fired.' This clearly separates it from sibling Reddit tools like get_reddit_campaigns or get_reddit_audiences.

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 explicit usage context: 'Relevant before conversion-optimized campaigns' and 'Every new ad group needs a conversion_pixel_id from here.' That is a clear when-to-use signal, though it names no alternative tool or exclusion case.

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