set-photo-metadata

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

With no annotations provided, the description fully discloses behavior: it is a WRITE tool requiring an env var, only modifies passed fields, never touches the image asset, validates photo existence, requires macOS Automation permission, and targets the open Photos library. This exceeds typical transparency.

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 well-structured with labeled sections (Use when, Returns, Do not use when, Safety). It is dense but every sentence adds value—no filler. Front-loading the purpose and usage makes it highly scannable.

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?

Despite the tool's complexity (write operation, safety flags, permissions, validation), the description covers all essential context: prerequisites, side effects, exclusions, return values, and operational constraints. Output schema info is supplemented by the description of returned fields.

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 coverage is 100%, so baseline is 3. The description adds beyond schema by explaining that empty string clears title/description, favorite is a boolean flag, and only passed fields are modified. This enriches parameter understanding beyond the schema's field descriptions.

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 purpose: 'set a photo's title, description, or favorite flag'. It names specific resources and actions, and explicitly distinguishes from siblings ('Do not use when: you want keywords — use set-keywords; or read metadata — use get-photo').

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 gives explicit usage guidance: 'Use when' lists concrete scenarios, and 'Do not use when' names alternative tools for exclusions. It also mentions prerequisites like the APPLE_PHOTOS_MCP_ENABLE_WRITES environment variable.

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