update_frontmatter

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

Annotations already indicate the operation is idempotent and non-destructive. The description adds meaningful behavioral details: merging semantics, preservation of unlisted keys, and automatic extension handling. It does not fully specify overwrite behavior for listed keys, but the added detail is valuable.

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?

Three concise sentences with the core action front-loaded and no filler. Every sentence contributes meaningful operational information.

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?

The core merge behavior is well covered, but the missing specification of the 'properties' string format is a significant invocation blocker. The simplicity of the tool partially offsets this, but the parameter format gap keeps it from being fully complete.

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. It indicates that 'properties' holds key-value pairs, but does not explain the required serialization format (JSON, YAML string, line-delimited, etc.). The 'path' parameter is also only clarified by the note about the automatic .md extension.

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 states a specific verb ('merge') and resource ('YAML frontmatter'), and adds behavior ('Unlisted keys preserved', '.md extension is added automatically'). This clearly distinguishes it from sibling content and file operations.

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 implies this tool is for updating frontmatter keys while preserving others, but it does not explicitly state when to use it versus alternatives or when not to use it. Sibling tools like append_to_note are implicitly different, but no routing guidance is provided.

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