run_functional_test_in_pie

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

Annotations already declare destructive/not-idempotent/not-readonly, but the description adds non-obvious behavior: the auto-add to the PrepareForPIE list and the "honest-gated" failure mode (success=false rather than an error on PIE start failure, with transport-drop handled separately). That is real value beyond the annotations. It stops short of explaining why the operation is destructive (e.g. PIE disrupts the editor world), which would be the final step to 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?

Front-loads the core action and prerequisite before the failure-mode note and return shape. Mostly tight, though the trailing return-value enumeration is a little dense and could arguably be trimmed; it nonetheless earns its place since no output schema exists.

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 output schema, the description correctly compensates by enumerating the return fields (test_asset_path, pie_started, verdict enum, pie_stopped, already_in_pie). Combined with the prerequisite and failure semantics, an agent has enough to call it correctly; only the alternative-tool routing is thin.

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%, and both parameters (test_asset_path, auto_stop_pie) are fully documented in the schema itself. The description echoes the asset-path concept but adds no syntax or format detail beyond the schema, so the baseline 3 applies.

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 (start a PIE session), the resource it acts on (the named AFunctionalTest BP), and the outcome (return the test verdict). This clearly separates it from siblings such as run_automation_test, start_play_in_editor, and wait_for_pie_completion, which an agent can now disambiguate without opening any 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?

It gives a clear prerequisite ("Requires the named BP to exist") and describes the PrepareForPIE mechanism, which is useful context. However, it never states when to prefer this over the many adjacent PIE/automation tools (start_play_in_editor, run_automation_test, wait_for_pie_completion), so usage is implied rather than explicit.

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