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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered. The description adds genuinely useful context beyond that: unchanged-vs-pending semantics ('never run on the site') and that merge conflicts are surfaced. It stops short of describing result shape or ordering, which keeps it out of the top band.

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 purpose, then the when-to-use, then the parameter contract — a sound order with no filler. It is one dense paragraph with em-dash asides that could have been broken out, but every sentence carries information.

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 no explanation here. For a two-optional-parameter read tool, the description covers purpose, timing, the sibling it precedes, and the workspace/container relationship — nothing an agent needs to invoke it correctly 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 0%, so the description must carry the load, and it does: workspace is described as a list_gtm_workspaces path with empty defaulting to the Default Workspace, and container as 'GTM-XXXX'/name to be used when workspace is empty. That inter-parameter dependency is exactly the kind of meaning the bare schema lacks, though format details like the full path shape remain implicit.

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States a specific verb and resource: shows pending (unpublished) changes in a GTM workspace, enumerating tags/triggers/variables that are added, updated, or deleted, plus merge conflicts. It is clearly distinguished from siblings like list_gtm_workspaces (which enumerates workspaces) and publish_gtm_container (which pushes them live).

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?

Explicitly names when to use it — before publish_gtm_container to preview what would go live — and gives a diagnostic use case ('why isn't my tag firing yet?'). It also explains the exclusion mechanism: unpublished changes never run on the site. Sibling routing is explicit rather than inferred.

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