Open WebUI MCP Server

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It states the tool posts a message, implying a write operation, but doesn't cover critical aspects like required permissions, rate limits, error handling, or what the output contains (though an output schema exists). This is a significant gap for a mutation tool with zero annotation coverage.

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?

The description is extremely concise—two short sentences that are front-loaded with the primary purpose and an optional feature. Every word earns its place with no redundancy or fluff, making it easy for an agent to parse quickly.

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?

Given the tool's moderate complexity (a write operation with nested parameters) and the presence of an output schema (which reduces need to describe returns), the description is minimally adequate. However, with no annotations and low schema coverage, it lacks crucial behavioral and parametric context, leaving gaps in understanding how to use the tool effectively.

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 0%, so the schema provides no parameter descriptions. The description adds minimal value by implying parameters for channel ID, message content, and optional parent ID, but doesn't explain their semantics (e.g., format of IDs, content constraints). With 1 parameter (a nested object with 3 sub-parameters), the baseline is 3 as it partially compensates for the schema gap but lacks detail.

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 clearly states the action ('Post a message') and target resource ('to a channel'), with an additional optional capability ('Optionally reply to a parent message'). It distinguishes from siblings like 'delete_channel_message' or 'get_channel_messages' by focusing on creation rather than retrieval or deletion. However, it doesn't explicitly differentiate from potential similar tools like 'create_channel' or 'share_chat', which keeps it from a perfect score.

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?

The description provides no guidance on when to use this tool versus alternatives. It doesn't mention prerequisites (e.g., needing channel access), exclusions (e.g., not for direct messages), or comparisons to siblings like 'create_channel' for channel creation or 'get_channel_messages' for reading messages. This leaves the agent with minimal context for decision-making.

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