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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds an approval-requirement note, but for a read operation it is vague boilerplate that never says whether reading values themselves is gated or whether this only concerns downstream workflow changes.

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 purpose is front-loaded in a single short sentence, which is good. The second sentence about MCP approval configurability does not obviously earn its place in a read-only lookup tool and reads as boilerplate noise.

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?

An output schema exists, so return values need not be described, and only one parameter is involved. However, the description never clarifies what 'custom values' actually contain (field keys, typed values) or whether results are scoped to the caller's permissions, leaving modest gaps for an agent to interpret.

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?

There is one required parameter (siteId) with 0% schema description coverage, so the description carries the burden of explaining it. 'A location's custom values' implies siteId identifies the location, but the exact identifier format (UUID, per the schema) and behavior for unknown sites remain unstated.

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 ('Read a location's custom values'), which maps clearly to retrieving custom field values for a site. It does not differentiate from plausible siblings such as list_custom_fields (field definitions) or set_site_custom_field (the write counterpart), which keeps it from 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?

There is no guidance on when to call this versus list_custom_fields or set_site_custom_field, and no prerequisites or exclusions are stated. The agent must infer from the name alone that this reads values rather than field definitions.

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