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

Adds genuine behavioral context beyond the annotations: the empty-list-plus-note behavior for public/other-org extensions, and how the returned tables are consumed at runtime via renderClient.getCustomTableData / upsertCustomTableData, plus a grounding pointer to lookup_command_frame. 'Read-only. Does not write files.' largely restates readOnlyHint, which is why this is a 4 rather than a 5.

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?

Front-loaded with the purpose and the runtime-consumption rationale before the constraints, and no filler sentences. It is a single dense paragraph with stacked parentheticals, which costs a bit of readability.

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?

No output schema exists, and the description compensates by describing the returned content (table name plus typed columns) and the empty-list case. Combined with annotations that cover the safety profile and a fully documented schema, an agent has everything needed to call and interpret this tool.

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 (hubToken, extensionId) are already documented in the schema, including the same 'id from a list_extensions result' note. The description adds no format, constraint, or edge-case detail about the parameters themselves, so the baseline 3 applies.

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?

Specific verb (List) plus resource (an extension's registered custom tables) with the return shape spelled out as 'table name + typed columns'. It also distinguishes itself from two siblings: flow_list_custom_tables (org's non-extension tables) and flow_list_extensions (source of the id). An agent can route correctly without opening any schema.

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?

Explicit prerequisites ('Pass the extension's id from list_extensions'), an exclusion ('Only the org's OWN extensions expose their tables'), and a named alternative for the other case ('the org's non-extension tables come from list_custom_tables'). It even states the outcome when the precondition fails: an empty list with a note.

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