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

Annotations already declare readOnlyHint=true and destructiveHint=false. The description adds useful context beyond the annotations: it returns a secure URL, may include an inline MCP image attachment, requires an API key, and has a $0.10 cost. This is valuable operational information without contradicting the 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?

The description is a single front-loaded sentence covering the core behavior, followed by a compact parenthetical with cost and auth requirements. Every clause contributes meaningful information; there is no 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 simple one-parameter read-only lookup, the description covers the return content, security property, attachment availability, cost, and authentication. An output schema exists, so enumerating metadata fields is unnecessary. Minor gaps include error handling and not-found behavior, but they are not essential for this simple tool.

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%, and the description does not explain photo_id at all—it doesn't state where the ID comes from, expected format, or how it relates to other photo endpoints. With only one parameter, the description should compensate for the missing schema docs, but it doesn't.

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 opens with 'Single photo metadata + secure URL,' which states a specific resource and operation. The 'Single photo' phrasing clearly distinguishes it from collection-oriented siblings like get_person_photos and search_photos.

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 retrieving one photo by ID, but it never states when to choose it over related siblings such as get_photos_for_event or get_photos_for_place. There is no explicit when/when-not guidance; the agent must infer usage from the tool name and the word 'Single.'

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