add_weigh_in

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

With no annotations, the description carries the full burden, and it does disclose a genuine behavioral fact: the client validates unit_key against {'kg','lbs'} and rejects anything else with a specific error. That is real value beyond the schema. It still omits other mutation-critical behavior — whether a date/time is assumed, whether re-submitting overwrites, and any auth requirements.

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 purpose is front-loaded and the docstring-style Args block is compact and easy to scan. The quoted error string is somewhat verbose but earns its place as a warning about a non-obvious validation trap.

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?

An output schema exists, so return values need not be explained, and the critical unit_key footgun is covered. But for a mutation with zero annotations, key facts are missing: the time/date semantics that distinguish it from add_weigh_in_with_timestamps and any indication of write scope or reversibility.

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 0%, so the description must compensate, and it largely does: unit_key is given its valid enum values ('kg' or 'lbs'), explicitly rules out the ambiguous 'lb', and quotes the validation error. weight is documented only as 'Weight value', which is thin but sufficient for a plain number.

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?

States a specific verb and resource ('Add a new weight measurement'), so the agent knows exactly what the tool does. However, it gives no differentiation from close siblings like add_weigh_in_with_timestamps or add_body_composition, which a reader cannot distinguish from the description alone.

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?

No when-to-use guidance and no alternatives named. The sibling add_weigh_in_with_timestamps is an obvious fork (does this one use the current time instead of supplied timestamps?) and the description never addresses it.

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