build_fix_message

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

The description discloses that BodyLength and CheckSum are computed automatically, which is a key behavioral trait. However, it does not discuss error handling, input validation, or behavior for missing/invalid fields. With no annotations, the description partially but not fully covers behavioral aspects.

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 a single sentence with an example, making it concise and front-loaded. It avoids unnecessary detail, but lacks structure such as bullet points or sections. Still, it effectively conveys the core action.

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?

Given 7 parameters and no output schema, the description is somewhat incomplete. It explains the core function but omits details on parameter defaults, allowed values for msg_type, or return format. The sibling tools provide some context, but more information would be helpful for correct invocation.

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%, so the description must add semantic meaning. It gives a high-level example (fields as name/value pairs) but does not detail parameters like msg_type, msg_seq_num, or begin_string. The fields parameter is vague ('anyOf object/null') with no further clarification.

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 action ('Build a FIX message') and resource ('from field names/values'). It provides an example ('Side=Buy') and notes computed fields (BodyLength, CheckSum). This distinguishes it from sibling tools (explain, parse, validate) which serve different purposes.

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 offers no guidance on when to use this tool versus alternatives like parse_fix_message or validate_fix_message. There is no mention of prerequisites, appropriate contexts, or exclusions, leaving the agent to infer usage.

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