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

Annotations already declare readOnly=true, destructive=false, openWorld=false, so safety is covered; the description adds real value on top with 'private', the $0.02 per-call cost, the API-key requirement, and the clarification that 'Actual photos stay separate' — telling the agent what it will and won't get back. It stops short of describing pagination or result limits, but the cost/auth disclosure is meaningful behavioral context.

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 short sentences, front-loaded with the core action, then the photo-separation caveat, then cost/auth. Every clause carries information; the trailing parenthetical cost/auth block is slightly telegraphic but not wasteful.

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 two-parameter read tool with an output schema (so return values needn't be explained), the description covers scope, ownership precondition, privacy, what is excluded (photos), cost, and auth. An agent has everything needed to decide and invoke 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?

Schema description coverage is 100%, so both parameters are already documented, including the enum values and the 'never create a duplicate' warning on entity_id. The description only echoes the entity types ('owned event, Inventory item or contact') without adding format or lookup semantics beyond the schema, so baseline 3 applies.

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 gives a specific verb and resource ('Read private Visual reference illustrations and provenance') and scopes it to three entity kinds that map exactly to the enum (event, inventory, person/contact). It does not distinguish itself from the near-named sibling get_food_visual_references, so an agent must still infer whether food visuals belong here, which keeps it below a 5.

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?

Usage context is implied by 'on an owned event, Inventory item or contact' — the agent learns this only works on records it owns — but there is no explicit when-to-use vs. alternative statement and no when-not guidance. The schema's note about reusing an existing entity_id adds a hint, but the description itself doesn't route the agent between this and the attach/get_food variants.

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