set_user_preference

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

With no annotations, the description must carry the full burden of disclosing behavior. It only says 'Store' and gives examples; it does not mention whether existing keys are overwritten, what the tool returns, or any prerequisites or side effects. This is a significant gap for a mutation operation.

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 two sentences, front-loaded with the core purpose, and includes a 'Use this when' clause. Every word earns its place with no redundancy or fluff.

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 low-complexity tool with a well-described schema, the description provides enough context to invoke it correctly. It gives clear usage triggers and examples. However, it omits behavioral details like overwrite semantics and return value, which would be relevant for a complete picture, but given the simplicity, the gap is minor.

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 baseline is 3. The description does not add significant meaning beyond the schema; its examples ('home' as key, 'Bristol' as value) merely mirror what the schema already provides, so no extra credit is earned.

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 function: 'Store a user preference like home/work addresses or other settings.' It uses a specific verb ('store') and resource ('user preference'), and gives concrete examples that distinguish it from the sibling get_user_preferences tool.

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?

It explicitly says 'Use this when the user wants to save a location for future use' and provides examples of when to apply it. However, it does not explicitly mention when not to use it or name the alternative getter tool as an exclusion, so it falls short of a 5.

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