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

Annotations already declare destructiveHint=true and readOnlyHint=false, and the description reinforces that by stating the operation REPLACES live content. It also adds genuinely new scope information — the organization and hosting account are left unchanged — which the annotations do not convey. Beyond that it discloses no permission requirements, build/queue behavior, or whether a failed redeploy leaves the site broken, so with annotations already covering the safety profile this lands at a solid 3 rather than a 4.

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?

Four compact sentences, front-loaded with the two mutually exclusive modes and followed by the destructive warning and the blast-radius note. Nothing is filler, though the parenthetical field lists inside the first sentence make it slightly denser than necessary.

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 and the annotations carry the safety profile, so the description doesn't owe return-value or safety detail. But for a 16-parameter mutation with 69% of parameters undocumented, the description should say more about how the build-related options interact with the two modes — currently an agent can invoke it but cannot reason well about the optional surface.

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 low at 31%, and the description compensates only partially: it explains the source_type/repo_url/archive_url grouping, the mutual exclusivity of version_id versus new code, and the private-repo path via pat_secret_name. The other optional parameters — branch, ref_type, env, import_type, framework, node_version, build_command, install_command, output_directory — get no treatment in either place, leaving an agent to infer defaults and interactions.

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?

Names a specific verb+resource ('Update an existing site') and spells out its two distinct modes: new code via source_type plus repo_url/archive_url, or redeploy of an earlier version_id. A sibling exists called revert_site_version whose purpose is close to the version_id path, yet the description never distinguishes the two, so an agent must guess between them.

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?

It gives a real precondition ('confirm with the user first' because live content is replaced) and points to list_site_deployments as the way to obtain a version_id. What is missing is routing: nothing says when to use this instead of deploy_site for fresh code or revert_site_version for rollbacks, which is the main ambiguity for an agent.

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