pin_message

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

Adds real context beyond the annotations: moderator-permission requirement, the default lifetime (until unpinned), that expired pins are cleared on the next background job run, and that an already-pinned message returns a note rather than an error. This aligns with idempotentHint=true. Missing rate-limit or failure-mode detail keeps it from 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-loads purpose and precondition, then uses clean Args/Returns sections. Every sentence adds information; nothing is redundant with the schema or annotations.

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 3-param mutation with a sparse schema, the description covers purpose, authorization, parameter formats, expiration behavior, and return shape. An output schema exists, so the return note is a bonus rather than a necessity.

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 0%, so the description carries the full burden and does so: it documents all three params, explains `until` as ISO 8601 with time zone, states its default semantics, and clarifies that `message_id` is the message to pin.

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 (pin) and resource (message) with scope ('to the top of the conversation for everyone'), which cleanly separates it from sibling unpin_message and from list_shared_items. An agent can identify the action without opening the 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?

Gives a clear precondition ('Needs moderator rights') and points to where the result surfaces (list_shared_items with item_type "pinned"). It does not explicitly name unpin_message as the inverse operation or state when not to pin, so it falls short of a full 5.

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