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

Goes well past the annotations: draft-save semantics, that it goes live on next publish_site and on live-mode sites the dashboard publishes only the code, that it never runs in the editor, the 20,000-character cap, stored-as-sent behavior, non-rejecting warnings, and that runOn applies immediately. The only notable gap is no statement about how the previous code is replaced (full overwrite per box) beyond the "" clearing note.

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?

One dense paragraph that front-loads what the tool does and where the code goes, then layers caveats. Every clause carries information, though the heavy parenthetical packing and run-on structure make it harder to scan than a bulleted split into "what it does / publication lifecycle / limits".

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 destructive, non-read-only mutation with no output schema, the description covers lifecycle (draft → publish), scope (all pages/layouts), limits, clearing, warnings, and the runOn permission constraint — everything an agent needs to call it correctly. The warnings return value is explained even though no output schema exists.

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 100%, so baseline is 3, but the description adds real semantics the schema lacks: only send the boxes you change, "" clears, runOn's default and immediate-application timing, and the agent permission restriction on runOn. It mostly complements rather than repeats the parameter docs.

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 (site-wide custom code) plus exact injection points: head before </head>, body before </body>, every page, every layout. It explicitly names the sibling it is not for (set_analytics_provider for plain GA4/Plausible/Fathom/Umami), so an agent can disambiguate without opening schemas.

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 positive use cases (tag managers, Clarity, ad pixels, chat widgets, verification tags) and an explicit alternative with condition: prefer set_analytics_provider for plain GA4/Plausible/Fathom/Umami. It also states partial-update behavior (send only the boxes you change, "" clears) and the permission constraint that draft-limited agents cannot set runOn.

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