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

Annotations already declare readOnlyHint=true, but the description adds meaningful behavioral detail beyond that: it explains that blocked is judged without running, that state mirrors the cockpit's empty-Leads verdict, that config is parsed with defaults filled, and that summary null means needs setup. It also confirms read-only behavior explicitly without contradicting 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?

The description is long but information-dense: every clause contributes a distinct field or semantic needed to interpret the response. It front-loads the most important usage signal ('the read to make before touching any of them') before detailed return fields. With no output schema present, this density is justified and not padding.

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?

Given the tool's rich response surface and the absence of an output schema, the description is remarkably complete: it covers per-lane fields, null semantics, blocked reasons, play-level state enum values, and quota details. An agent has enough context to invoke the tool and interpret its full result.

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?

The input schema fully documents the single parameter, playId, including where it comes from ('from gtm_list_plays'), so schema coverage is 100%. The description adds no parameter-specific detail, which is acceptable because the schema alone carries the necessary meaning; per the rubric this is baseline 3.

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?

The description clearly identifies the resource (all five sourcing lanes of a play) and the operation (showing/reading them), including the distinction that it covers configured or unconfigured lanes. It names itself as the read to make before touching any lane, separating it clearly from sibling mutation tools like gtm_configure_source, gtm_set_source, and gtm_run_source.

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 'the read to make before touching any of them' provides explicit guidance on when to call this tool: as a preparation step before mutation or execution. It does not enumerate exclusions or directly compare against alternatives like gtm_show_play or gtm_source_runs, but the positional guidance is clear enough for an agent to select it appropriately.

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