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

Annotations already establish this is a safe read-only, non-open-world call, so the bar is low. The description adds real behavioral context: it is a conversational disambiguation step that should ask the user a question, and it discloses a capability limit ('Qualified briefs are not open yet'). It stops short of stating what the call returns or that it stores nothing, but that gap is minor given the annotations.

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-loaded with 'Start here' and then the two paths in order; every sentence carries routing or scope information and none is filler. It is slightly dense in the agency-path clause but still compact and readable.

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 router tool with one optional parameter, no nested objects, and no output schema, the description supplies what an agent needs: when to invoke it, the two branches, and the follow-up tool for each. It does not mention that the call returns no listing data itself, a minor omission only.

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% and the single user_request parameter is fully described in the schema. The description implies capturing the user's intent but adds no syntax, length, or formatting meaning beyond it, so the 3 baseline 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 opening 'Start here' plus the two-path routing statement makes it unmistakable that this is the entry-point/disambiguation tool rather than a data fetcher. It explicitly names the sibling tools each path leads to (search tools, join_as_agency), so an agent can distinguish it from get_agency, search_agencies, and join_as_agency without opening a 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?

It gives an explicit branching condition: brand looking for an agency vs. agency wanting to join. Each branch names the concrete follow-up tools, and it adds an exclusion ('Qualified briefs are not open yet') so the agent knows not to attempt that path.

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