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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds a key behavioral trait by stating it 'remember[s] it for future conversations', indicating persistent internal knowledge. This does not contradict the annotations, as the memory change is internal and non-destructive.

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?

Two short sentences with the most important information front-loaded. There is slight redundancy between 'Learn Expo how-to...' and 'Use this to teach the assistant', but no filler or unnecessary detail.

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 simple one-parameter tool with helpful annotations and no output schema, the description adequately covers the purpose and the unique memory behavior. It lacks guidance on how the learned knowledge is applied or when to prefer this over documentation tools, but the overall simplicity lowers the burden.

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 compensate, but it only says 'specific topic' without mentioning the enum or that the only supported value is 'expo-router'. The schema itself constrains the parameter, but the description adds no value beyond what the schema already provides.

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 uses a specific verb 'Learn' with a clear resource ('Expo how-to for a specific topic') and explicitly states the tool is for teaching the assistant. This differentiates it from sibling tools like expo_read_documentation and expo_search_documentation by emphasizing the 'remember it for future conversations' aspect.

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?

Provides clear context on when to use: 'Use this to teach the assistant about specific Expo features or workflows'. However, it does not explicitly mention alternatives or when not to use it compared to documentation read/search tools, which are obvious siblings.

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