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

Annotations already declare readOnlyHint=false, idempotentHint=true and destructiveHint=false, so safety is covered. The description adds value beyond them by disclosing the permission requirement (workspace owner) and the replacement semantics of origins, though it says nothing about validation failures or what an invalid hostname does.

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 front-loaded sentence with the verb first and the permission constraint trailing; the parenthetical for the optional flag is efficient. No sentence is wasted.

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 3-parameter mutation tool with no output schema, the description covers purpose, auth requirement, and replace-not-merge semantics, and the dev parameter's schema text clarifies that origins are bare hostnames without ports. The remaining gap is hostname format details (wildcards, schemes) and error behavior.

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 67%: origins and dev already carry descriptions, and key_id is undocumented in both places. The description reinforces the full-replacement semantics and flags dev as optional, but adds no format guidance (scheme, port, wildcard) 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 names a precise verb ('Replace') and a precise resource ('the hostnames a publishable key may be used from'), plus the optional dev flag. It is unambiguously distinct from the key-management siblings (create_key, revoke_key, list_keys) without needing to name 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?

'Workspace owner only' supplies a real prerequisite for calling it, and 'Replace ... the full new list' establishes that this is an overwrite operation rather than an append, which is the key usage distinction. It stops short of naming alternatives or when-not-to-use cases, so it falls just short of a 5.

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