Check custom data type name existence

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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is known. The description adds that this is a pure existence check, but does not disclose any additional behavioral traits such as return format, case sensitivity, or partial matching behavior. No contradiction.

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 sentence, 18 words, front-loaded with the action. Every word earns its place; no fluff or repetition.

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 simple 1-parameter predicate tool with read-only annotations, the description is adequate. It states what it checks and the target resource. It does not mention the return value, but the tool name and description strongly imply a boolean result; given the simplicity, this is acceptable.

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 single parameter udtName is fully described in the schema (100% coverage), with the description 'The name of the custom data type to check for existence.' The tool description adds no extra parameter semantics beyond this, so baseline 3 applies.

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 uses a specific verb ('Checks whether') and clearly identifies the resource (custom user data type name existence). It distinguishes itself from sibling tools like custom_column_data_types_list (which lists types) and custom_column_udt_length (which returns length) by focusing on existence checking.

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 implies the tool is for verifying existence of a custom data type name before other operations, but it does not explicitly state when to use it vs alternatives or mention any exclusions. The context is clear from the phrasing 'is already defined in the system.'

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