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

Annotations already cover the read-only/idempotent/safe profile, and the description goes well beyond them: it discloses that the lookup is performed per Telegram account, enumerates the returned fields (title, kind, members, owning account, thread_id), points at messages.read_history to read a kept thread, and warns that mutual-only visibility is a hard Telegram limitation.

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 tight paragraphs, front-loaded with the core purpose and no filler; the identifier sentence and the visibility caveat each carry information an agent needs. Slightly long for the payload but nothing is redundant.

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 present, the description compensates by enumerating the returned fields and the follow-up read path, and it flags the visibility boundary. Combined with full parameter coverage and read-only annotations, an agent has everything needed to call it correctly.

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 the baseline is 3, but the description adds real meaning on top of the per-parameter text by presenting contact_id / telegram_user_id / username as a mutually exclusive set of alternative identifiers and tying contact_id to contacts.find's entity_id. It does not describe in_workspace semantics beyond 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 precise verb+resource: lists every group and channel a person shares with us, framed as Telegram's own 'groups in common' list queried across each workspace Telegram account. This is distinct from siblings like contacts_profile, channels_contacts and group_list, so an agent can pick it 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?

Explains which of the three identifiers to pass and notes the structural limitation that groups none of our accounts are in are invisible. However, it never states when to prefer this over contacts_profile, channels_contacts or group_list, so tool-level routing is left to inference.

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