Create External ID Field

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

Annotations already indicate this is a write operation (readOnlyHint=false), non-destructive (destructiveHint=false), and idempotent (idempotentHint=true). The description adds useful behavioral detail: 'The field is also automatically marked as unique.' This goes beyond what annotations provide and informs the agent of an important side effect, without contradicting any annotation.

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 concise and front-loaded. The first sentence immediately states the tool's purpose, followed by a compact bullet-style list of parameters. Every sentence earns its place, with no fluff or repetition of the tool name. The structure is easy to scan and digest.

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?

The tool is moderately simple with six well-documented parameters and no output schema. The description covers the core purpose, key behavioral side effect (auto-unique), and use case. However, it omits potential prerequisites (e.g., object existence, field name uniqueness) and error handling. Despite these gaps, the annotations and schema fill in enough that the description is nearly complete.

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 100%, so the baseline is 3. The description repeats parameter names with brief explanations (e.g., 'fullName: field API name ending in __c'), but these add minimal value over the schema's own detailed descriptions. The only slight addition is clarifying that 'length' is for Text fields, but this is also inferable from the schema's maximum/minimum constraints. No new semantic relationships are described.

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 'Creates a custom field with externalId=true on a Salesforce object,' which is a specific verb+resource combination. It distinguishes itself from sibling tools like sf_create_custom_field by emphasizing the externalId=true and unique field characteristics, leaving no ambiguity about its purpose.

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 provides clear context for when to use the tool: 'External ID fields can be used for upsert operations and integration matching.' This indicates the intended use case. However, it does not explicitly name alternative tools or state when not to use this tool, so it falls 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.