yazio-mcp

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

Annotations indicate this is a non-readOnly, non-idempotent tool (mutation with side effects), which the description aligns with by implying data modification ('Log a water intake entry'). The description adds valuable context beyond annotations by specifying the required cumulative calculation process, though it doesn't detail potential errors, rate limits, or authentication needs. No contradiction exists.

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 front-loaded with the core purpose in the first sentence, followed by essential usage instructions. Both sentences are necessary and efficient, with no redundant information. It's appropriately sized for a tool with two parameters and clear behavioral context.

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 the tool's complexity (mutation with a specific calculation process), annotations cover safety hints, and schema fully describes parameters, but there's no output schema. The description compensates well by explaining the cumulative calculation requirement, though it could mention the return value or error handling. It's largely complete but has minor gaps.

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 100%, so the schema already fully documents the parameters (date format, water_intake as cumulative ml). The description reiterates the format and cumulative nature but doesn't add significant semantic details beyond the schema, such as validation rules or edge cases. Baseline 3 is appropriate given high schema coverage.

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 specific action ('Log a water intake entry') with the resource ('water intake') and distinguishes it from sibling tools like 'get_user_water_intake' (which retrieves data) and 'add_user_consumed_item' (which handles different consumables). It precisely defines the tool's function without being vague or tautological.

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 explicit guidance on when to use this tool by stating 'Always get the latest water intake first and add the new amount to calculate the cumulative value,' which implies an alternative approach (using 'get_user_water_intake' before this tool) and clarifies the prerequisite step for correct usage. It effectively distinguishes this from read-only siblings.

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