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

With no annotations, the description carries the burden. It communicates read-only intent ('Retrieve') and adds performance/scope context ('efficiently', 'without fetching all custom data'), which is useful. It does not address error conditions or return format, but for a simple read operation this is acceptable.

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 with no filler. Every word earns its place by conveying the action, scoping, and efficiency benefit.

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?

Adequate for a simple read tool: it explains the core function and performance tradeoff. However, there is no output schema and no explicit mention of return format or error behavior, and it does not directly compare with getCustomDataForEntity, leaving some gaps.

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 covers 2 of 3 parameters; 'key' lacks a description. The tool description clarifies that 'key' refers to a custom data attribute key, but adds little beyond what the schema already provides for tagOrId and context. With 67% coverage, the description only partially compensates.

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 a specific action ('Retrieve a specific custom data value by key for an entity') and differentiates from siblings by emphasizing 'without fetching all custom data'. This makes the tool's purpose unambiguous and distinct from getCustomDataForEntity.

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 the appropriate use case (single attribute lookup) and contrasts with bulk retrieval via 'without fetching all custom data'. However, it does not explicitly name the sibling tool or state when not to use it, so it stops short of a 5.

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