write

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

Annotations provide only idempotentHint. Description adds critical details: automatic parent directory creation, full content overwrite, specific errors (EISDIR, EINVAL). This goes well beyond annotations.

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?

Description is brief (three sentences), front-loads the action, and efficiently adds necessary details without filler.

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 tool with 3 params and no output schema, the description covers behavior (create, overwrite, auto-mkdir), error cases, and storage semantics. Complete enough for an agent to use correctly.

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?

Input schema covers all parameters with descriptions (100% coverage). Description adds marginal value by specifying path is absolute and store is for cross-session, but these are already in schema.

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?

Description clearly states 'Write content to a file, creating it if it doesn't exist.' It uses a specific verb ('Write') and resource ('file'), and distinguishes from sibling 'append' by implying overwrite behavior.

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?

Description provides behavioral context (creates parent dirs, overwrites completely) and error conditions. It doesn't explicitly state when to use this vs sibling tools like 'append', but the overwrite behavior is clear.

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