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

Annotations already establish a safe read-only, non-destructive profile. The description adds genuinely useful context beyond them: results are inline MCP images with per-asset render status, the avatar is ordered first, paging is capped at six, cost is $0.10, and an API key is required. That covers output shape, ordering, and auth/cost constraints the annotations do not.

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 tight sentences, front-loaded with what is returned before paging and pricing details. Every clause earns its place; the cost/auth parenthetical is compact. Slightly dense but 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?

Because an output schema exists, return-value documentation is not required. The description still covers output format, ordering, pagination, auth, and cost, leaving only the semantic gap on person_id, which is minor given the tool name.

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 carries the burden. It explains offset (paging) and the six-per-call ceiling, which maps to the limit parameter's maximum of 6. person_id is left unexplained, but it is self-evident from the tool's purpose, so partial compensation is reasonable.

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?

States a specific verb and resource: reads a contact's avatar and gallery. This clearly separates it from get_photo (single asset), search_photos, and get_photos_for_event/place, though it does not name those siblings explicitly. The scope ('avatar and gallery') is precise enough for an agent to route correctly.

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 operational guidance ('Use offset to page through photos (up to six per call); never paste raw image URLs into chat'), which tells the agent how to consume results. However, there is no when-to-use vs when-to-use-something-else guidance relative to get_photo, search_photos, or get_entity_assets, so selection is left implicit.

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