discord_create_thread_from_message

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

Annotations already declare readOnlyHint=false, idempotentHint=false, and openWorldHint=true, and the description adds genuinely new context on top: the mutation is not idempotent, the result should be checked before retrying, and specific bot permissions (Create Public Threads, View Channel, Read Message History) may be required. What it doesn't disclose is failure modes such as what happens if a thread already exists on that message, beyond the implicit ID collision rule.

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?

Four tight sentences, front-loaded with the core action, followed by the ID constraint, the channel exclusion, the sibling alternative, permissions, and the retry caveat in descending order of importance. Nothing is padded and no sentence merely restates the tool name.

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?

An output schema exists, so return-value explanation is not needed, yet the description still notes it returns the created thread. Combined with the permission list, exclusivity rule, and non-idempotency warning, an agent has everything required to invoke this mutation 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 description coverage is 100%, so all six parameters (including the enum-constrained auto_archive_duration and rate_limit_per_user) are already documented in the schema. The description adds no parameter-level detail — it does not explain the relationship between channel_id and message_id or the name length bound — so the baseline of 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?

The description opens with a specific verb+resource ("Create a new public or announcement thread from an existing message") and immediately distinguishes this tool from the sibling discord_create_thread, which creates standalone threads. The channel-type constraint and the one-thread-per-message rule make the scope unambiguous.

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?

It states both when to use this tool (branching a thread off an existing message) and when to use the alternative ("To create a standalone thread without a starter message, use discord_create_thread"). It also names exclusion conditions — not supported in forum or media channels — so the agent can rule out incorrect calls.

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