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

Annotations already establish readOnly, idempotent, non-destructive behavior, so the bar is lower; the description adds genuinely useful domain behavior — the one-MTProto-call-per-account limit and the pre-flight role of the call — which no annotation conveys. Return payload shape is not described, but that is a minor omission for a filtered list.

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, zero filler, with the listing scope front-loaded and the usage rationale immediately after. Every clause earns its place.

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 zero-required-parameter read-only list tool, the description covers purpose and the exact decision it supports. With no output schema, the returned call fields are left unstated, a small gap but not one that blocks correct invocation.

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%, and the channel, in_workspace, and channel_account_id descriptions already explain filtering and the per-line busy check. The description adds no parameter syntax or semantics beyond the schema, so 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?

States a specific verb and resource with scope: 'List active voice calls in this workspace.' The qualifier 'active' distinguishes it from history-style siblings, and the description ties it to a concrete decision (is the line free) rather than restating the name.

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?

Gives explicit when-to-use: run it before calls.make on a Telegram account, and explains the governing constraint (only one MTProto call per account at a time). It does not name when-not to use it or point to a listing alternative such as calls_list_history, which keeps it short of a 5.

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