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

Annotations already declare this as a non-read-only, non-destructive write, so the safety profile is covered. The description adds real value with the name regex and subaccount-uniqueness constraint, but says nothing about permissions/auth, what happens on duplicate names, or what creating a custom tool requires (URL, method, etc.).

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?

Two tight sentences, front-loaded with the core action and followed by the key validation constraint. No filler.

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 tool with 7 undocumented parameters, nested objects, an enum, and no output schema, the description is far too thin. An agent cannot tell what fields like url, httpMethod, or parameters mean or how to shape them, so it would have to guess.

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 description coverage is 0% across 7 parameters, including a nested 'parameters' array and an httpMethod enum, so the description must carry the burden. It only annotates the 'name' parameter (format + uniqueness) and leaves url, httpMethod, headers, parameters, description, and subAccountId entirely unexplained.

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 clear verb and resource ('Create a custom tool') and pins down the toolType, so an agent knows this is the creation counterpart to tools_update/tools_delete. It stops short of describing what a custom tool actually is (an HTTP-backed endpoint), so it is not fully differentiated in substance.

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?

No when-to-use guidance, prerequisites, or contrast with siblings such as tools_update or search_tools. The intended usage is only implied by the tool name.

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