iso_decode_mti

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

With no annotations, the description carries full burden. It discloses that the tool decodes into four components and provides special behavior for request messages. However, it does not mention auth needs, rate limits, or side effects, though as a decode operation these are minimal.

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 sentences, front-loaded with the main function, then a useful additional detail. No wasted words.

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 decode tool with one parameter and an output schema (not provided but assumed), the description explains the decoding result and request-response behavior. It does not detail output format, but the existence of an output schema mitigates that.

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 the schema already describing the mti parameter as a 4-digit ISO 8583 MTI string with pattern and length constraints. The tool description repeats '4-digit MTI' but adds no new semantic information beyond what the schema provides.

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 it decodes a 4-digit MTI into version, message class, function, and origin. The verb 'Decode' and resource 'MTI' are specific, and the tool distinguishes itself from siblings like iso_lookup_field.

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 a specific usage hint: for request messages (function digit = 0), it returns the expected response MTI. This helps the agent understand a special case but does not explicitly state when to use this tool over alternatives or when not to use it.

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