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

Annotations already flag this as destructive and non-read-only, and the description adds context beyond them: the whole prompt is overwritten rather than patched, live agents are rejected with a publishUrl instead of an edit, and the prior instructions are returned so the change can be reverted. That is a real gain over the structured hints, missing only detail on permissions or validation failures.

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?

Three sentences with no filler: what it does, when it works, and what it returns. The blocker for live agents is stated up front, before the return behavior.

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?

Complete for a two-parameter replacement tool. The output schema covers the return shape, and the description adds the important non-obvious behavior: live agents are rejected and return a publishUrl, and the previous instructions come back for revert.

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%, and both parameters are already documented in the schema, so the baseline is 3. The description adds no format or length guidance beyond the schema, although 'entire instructions, not a diff' slightly reinforces what is already there.

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?

Uses a specific verb + resource: 'Replace a private agent's entire instructions (its system prompt)'. It scopes to private agents, which separates it from tools like get_agent or create_agent without ambiguity.

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 an explicit precondition ('Only agents that aren't live on the web can be changed here') and tells the agent what to do otherwise (use the returned publishUrl to take it offline). No sibling tool is named as the alternative, 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.