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

Read-only annotations mean the safety bar is already met, and the description adds genuinely useful behavioral context: row granularity, the columns returned, and the note that deliverySeconds surfaces greylisting/throttling before placement numbers move. That is real operator context beyond the annotations.

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?

Two sentences, front-loaded with the row semantics, then a focused tip about deliverySeconds. No filler, though the second sentence is somewhat advisory rather than structural.

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?

For a single-param read tool with no output schema, the description covers granularity and key fields adequately, and the annotations cover the safety profile. It stops short of pagination or return-value shape details, but nothing essential for a correct call 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% and the single id parameter is well documented in the schema itself, including the source list_inbox_placement_runs. The description adds no syntax or format detail beyond that, so baseline 3 is correct.

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?

Specific verb ('Returns one row per probe email'), specific resource (probe results of a run), and explicit row granularity. An agent can tell it apart from get_inbox_placement_run and list_inbox_placement_runs without opening either schema.

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 id description routes back to list_inbox_placement_runs, implying this is the drill-down step. However, no explicit when-to-use versus get_inbox_placement_run or get_inbox_placement_stats_by_date, and no stated prerequisite that a run must have completed.

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