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

Annotations are minimal (readOnlyHint=false, destructiveHint=false, openWorldHint=false) and do not convey meaningful behavioral detail. The description only repeats the action ('attach') without disclosing side effects, prerequisites, reversibility, or failure conditions. An agent is left to infer that attaching is a persistent linkage operation without additional 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?

One sentence, no filler, front-loaded with the action. Every word contributes to the core message. The description is appropriately sized for the tool's simplicity.

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 low-complexity tool with two well-documented parameters and no output schema, the description is sufficient to convey the purpose and allow correct invocation. It does not mention edge cases or side effects, but these are not critical given the simple attach operation and minus number of parameters.

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 coverage is 100%, so both parameters (agent_id and endpoint_id) already have descriptions in the input schema that explain their provenance (list_agents, get_catalog). The tool description does not add any parameter-specific information beyond what the schema provides, so it meets the baseline of 3.

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 ('Attach'), a specific resource ('existing custom API-endpoint tool'), and the target ('the agent'), which is clear and unambiguous. It explicitly differentiates this from sibling attach tools (attach_mcp_server, attach_ai_tool, etc.) by naming the API-endpoint tool type, so an agent can confidently select it.

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 makes the resource type explicit ('existing custom API-endpoint tool'), which implies it should be used when the user wants to attach an API endpoint. It does not, however, provide explicit 'when not to use' guidance or name alternatives, leaving some inference to the agent. Given the clear resource classification among many attach siblings, this is adequate.

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