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

Adds substantial context beyond the annotations: host-dependent behavior (works on stdio/CLI, not fixed-roster hosts), reply semantics ('says so in its reply rather than reporting a success you cannot use'), and safety/cost profile ('Free, instant, and it never turns anything off'). This is consistent with idempotentHint=true and destructiveHint=false while enriching both.

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?

Long, but nearly every sentence is load-bearing: host caveat, alternative route, trigger rules, valid values, and safety reassurance. The size rationale for held-out groups runs somewhat long ('most of the total schema weight across eleven ad platforms') and is mildly redundant with 'Most sessions need neither,' keeping this from a 5.

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 1-parameter tool with no output schema, this covers everything needed to invoke correctly: what it does, when to call it, valid values, the host-compatibility failure mode, and reply behavior on failure. The only omission is the exact shape of a success reply, which is minor given the tool's simplicity and the explicit disclosure of its failure mode.

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 schema has 100% coverage but only provides one example value ('ads') and no enums. The description supplies the complete valid-value vocabulary: 'core, research, create, channels, channel_admin, analytics, ads, files, workspace — or all' — which an agent cannot derive from the schema. It also ties specific parameter values to triggering conditions, making the parameter semantics actionable.

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 opening sentence states a specific verb and resource: 'Switch on a group of tools that is not in this session's roster.' It clearly differentiates this tool from the 170+ siblings, none of which manage tool availability — they are all content, posting, listing, or CRUD operations. No ambiguity about what this meta-tool does.

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?

Gives explicit when-to-call rules with concrete payloads: 'If the user asks to build, budget, target, report on or change an ad campaign on any platform, call enable_tools({groups:['ads']}) first' and an analogous rule for analytics. It also names the alternative route ('`?tools=all` on the server URL') and the condition where this tool won't work (fixed-roster hosts like ChatGPT).

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