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

Annotations already declare readOnlyHint=false and idempotentHint=true, so the description need not restate those. It adds useful context by telling users to use add/remove arrays for granular subcollection control, implying that arrays are additive/removal rather than direct replacement. However, it does not explain idempotency or detail partial-update behavior beyond that.

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?

The description is two sentences, front-loaded with the main purpose, and every word adds value. It avoids restating schema fields and quickly communicates both scope and a key usage pattern.

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?

Given the complexity of 14 parameters across multiple subcollections, the description does a good job of summarizing the tool's scope and the add/remove pattern. The schema handles individual parameter details, so the description does not need to list them. It could mention that only provided fields are updated, but the schema and idempotentHint cover most context.

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% description coverage for all 14 parameters, so the schema already provides parameter meaning. The description adds minimal semantic value beyond grouping parameters into categories (config, skills, tools, extensions) and mentioning the add/remove pattern. This matches the baseline for high schema coverage.

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 clearly states the tool's function: 'Update any part of an agent: config, skills, tools, or extensions.' It uses a specific verb and resource, and the enumeration of updateable areas distinguishes it from sibling tools like create_agent or delete_agent.

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?

The description establishes that this tool is for updating existing agents and covers config, skills, tools, and extensions. It does not explicitly mention alternatives like create or delete, but the clear scope and sibling tool names provide enough context. The instruction to 'Use add/remove arrays for granular control' offers practical guidance for subcollections.

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