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

Annotations already cover readOnly, idempotent and non-destructive semantics, so the description need not restate safety. It adds genuine value beyond the structured data by disclosing what is returned (name, when-to-use text, method, URL, headers, body template, inputs, active flag, last test, site login) and a security-relevant constraint: secrets are never returned, only whether one is stored.

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?

Two sentences, front-loaded with the verb and resource, and every clause earns its place either by enumerating return payload or by pointing at the id source. The long field list is compressed into a single sentence rather than padded prose.

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?

With no output schema, the description supplies the return-value inventory an agent needs, while error semantics live in the input schema and the safety profile in the annotations. Nothing required to call a 2-parameter, read-only getter correctly is missing.

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%, including error semantics for both uuid parameters (404 not_found, 404 agent_not_found, 403 agent_not_authorized), so the schema does the heavy lifting and the baseline is 3. The description contributes only the origin of tool_id via list_custom_api_tools, a small addition over 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?

States a specific verb and resource with scope ('Get one custom API tool of an agent') and enumerates exactly which fields are returned, so the agent knows what the call yields. It also routes the agent away from guessing the id by pointing at the sibling list_custom_api_tools.

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?

Provides a clear prerequisite and routing hint ('Get its id from list_custom_api_tools'), which effectively tells the agent when this tool applies versus the listing sibling. It stops short of explicitly stating when not to use it (e.g., vs. list_custom_api_tool_runs or update_custom_api_tool), so it is not a full when/when-not treatment.

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