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

Annotations only declare readOnly=false, destructive=false, openWorld=true; the description adds genuinely new behavior: a 10000 magnitude cap, acceptance of negative values, absence of a delete endpoint, and the resulting non-round-trippable state. That is real value beyond the annotations, though the same 'no delete endpoint' fact is stated twice.

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?

Only three sentences, but 'There is no delete endpoint' is repeated verbatim and the bolded 'not safely round-trippable' is jargon that adds little for an agent. The unit/negation semantics are front-loaded, so the waste is at the tail.

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 single-value mutation with no output schema, the description covers mutation semantics, the cap, and the irreversibility of entries, which is what an agent needs to call it safely. Missing only explicit defaulting behavior for the optional when/cdate fields.

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 67% and the one undocumented parameter, valueInMl, is precisely the one the description explains (raw milliliters, cap 10000, negatives allowed). It does not address the when vs cdate distinction, but the schema already documents both of those.

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 ('Logs water intake') plus the unit (milliliters), which an agent can distinguish from the read-side sibling get_hydration_data without opening a schema.

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?

Gives actionable guidance on how to correct an entry ('negative values subtract') and warns that no delete endpoint exists, which effectively tells the agent when this tool is the only option. It stops short of naming a sibling or stating an explicit when-not condition.

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