Find a direct-message space

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

The annotations already signal read-only, idempotent, and non-destructive behavior, and the description adds valuable context beyond those: it returns HTTP 404 when no DM exists, it cannot create DMs, and it accepts multiple user identifier formats. This gives an agent accurate expectations about failure modes and limitations.

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 sentences with no filler. The core behavior is front-loaded first, followed by the critical 404 limitation, and then the accepted input formats. Every sentence adds necessary information for correct invocation.

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 simple single-parameter tool, the description covers the return value, the error case, the creation limitation, and the accepted user identifier syntax. No output schema exists, so the inline explanation of the returned space name is sufficient for an agent to chain the result into send_message.

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 schema already fully documents the single 'user' parameter. The description repeats the accepted identity formats and adds that the user is the counterpart of the authenticated user, which is useful but not essential 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 specific verb and resource: it finds the EXISTING direct-message space between the authenticated user and another user, and clarifies it returns the space name for use with send_message. This clearly distinguishes it from siblings like get_space or search_spaces because it targets DM lookup by user.

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?

Explicitly explains both when to use the tool (finding an existing DM space to send a message into) and when not to use it (when no DM exists, since it cannot create one). It names the alternative path — spaces.setup via raw_request — making the decision boundary clear.

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