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

With no annotations provided, the description carries the burden of behavioral disclosure. It mentions that the tool 'Works in both directions' and instructs to use 'ieUnit' as the unit code. However, it does not disclose potential side effects (e.g., whether it modifies any data), error conditions, or return format. For a conversion tool, the read-only nature is implied but not explicitly stated, leaving some ambiguity.

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 three sentences, front-loaded with the primary purpose. It delivers essential information without unnecessary detail. Every sentence contributes: purpose/scope, directionality and example, and a pointer to sibling tool. This is a model of concise, structured tool documentation.

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 three required parameters, no output schema, and no annotations, the description covers the essential operational aspects: unit types, direction, and how to obtain codes. It lacks some details like error behavior or exact return structure, but given the simplicity and the existing schema, it is sufficiently complete for an agent to invoke the tool correctly.

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% with each parameter described. The description adds value beyond the schema by providing concrete examples ('250 CHF to ieUnit') and clarifying the 'ieUnit' code usage. This reinforces the schema and helps the agent understand valid inputs, going beyond the basic parameter descriptions.

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: 'Convert an amount between the ieUnit and about 60 other units'. It specifies the types of units (fiat, crypto, gold, silver, XIN) and provides concrete examples. It also distinguishes from sibling tools by mentioning ieunit_basket for retrieving unit codes.

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 on when to use this tool: for conversions between ieUnit and other units. It explicitly references an alternative, telling the user to 'Call ieunit_basket first if you need the list of available unit codes.' This guidance helps an agent choose the right tool but does not explicitly state when not to use this tool relative to other siblings like compare or history.

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