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

The readOnlyHint annotation already establishes this as a safe read operation. The description adds that the lookup is scoped to a connection and uses a numeric contact id, but it does not add behavioral context such as error behavior, permissions, or response characteristics.

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 two short sentences, front-loads the operation, and includes the endpoint without unnecessary filler. Every sentence contributes to identifying the tool.

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, read-only get-by-id tool with full schema coverage and annotations, the description is largely sufficient. It could mention the return value more explicitly since no output schema exists, but the operation itself is clear.

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 well documented in the schema. The description slightly reinforces that the contact is identified numerically and belongs to a connection, but it does not add meaningful semantics beyond the schema.

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 states a specific verb and resource: 'Get one contact of a connection by its numeric id.' It clearly distinguishes this from bulk contact listing by emphasizing a single contact and numeric id, though it does not explicitly name the sibling tool it replaces.

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 usage when retrieving a single contact by numeric id, but it does not explicitly say when to choose this over list_contacts or how to obtain the required hash_key and id. There are no exclusions or alternative-tool guidance.

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