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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds a meaningful non-obvious constraint: the list is limited to containers "enabled for AI", implying the result is a filtered subset rather than every container in the account. It omits pagination and the fact that openWorldHint implies the live result may vary, but relative to the annotation coverage this is solid.

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 short sentences, front-loaded with the resource and result fields, then the "start here" routing cue. No filler, though the value does not justify stretching to a fifth point.

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?

This is a simple read-only list tool with three fully documented optional parameters and annotations covering its safety profile, so the description is nearly sufficient. It could go further by clarifying whether the AI-enabled filter can be bypassed or how results are ordered, but nothing an agent needs in order to call it 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 description coverage is 100% and both enums (detail, language) are fully documented in the schema, so the baseline of 3 applies. The description only marginally reinforces semantics by tying "client folders" to the folder parameter and by implying the returned identifiers, without adding format or defaulting detail beyond the schema.

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 pairs a specific verb ("List") with a specific resource ("Google Tag Manager containers") and enumerates the useful fields returned (public IDs like GTM-XXXX, accounts, client folders). It does not name a sibling such as gtm_overview or gtm_audit, so the boundary between listing containers and the other GTM read tools is left to inference.

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?

"Start here for Tag Manager questions" gives a clear entry-point cue, which is real routing guidance. However, no exclusions or alternatives are named -- an agent cannot tell from the description when it should go to gtm_overview, gtm_tag_details, or gtm_pending_changes instead.

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