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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower, and the description still adds two useful behavioral facts: results come back 'oldest first', and each item exposes its site's login but with the login's secrets stripped. That redaction detail is exactly the kind of context annotations cannot convey.

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?

Three short lines, with the ordering and login-redaction details front-loaded rather than buried. The first line is a verbatim restatement of the title and earns nothing, but the remaining two lines are dense and waste-free.

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 one-parameter list tool with no output schema, the description is adequate: it discloses result ordering and part of the item payload (login without secrets). It says nothing about pagination, result limits, or whether an empty list is possible, which matters for a tool whose return shape has no schema to fall back on.

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% and the single agent_id parameter is documented in the schema with its 404/403 failure modes. The description contributes nothing about the parameter, so the baseline of 3 is appropriate.

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 (List) and resource (an agent's custom API tools), and the second line clarifies what these tools represent ('what its AI can do with your own system'). It is clear, though it never explicitly distinguishes itself from the close sibling list_custom_api_tool_runs, leaving the agent to infer 'tools' vs 'runs'.

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 never states when to use this tool versus alternatives, nor any preconditions. With roughly a dozen list_* siblings in scope, the absence of any routing guidance is a real gap beyond a mere implied 'use this to list things.'

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