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

Annotations already declare readOnly, openWorld, idempotent, and non-destructive behavior thousands of times, so the bar for extra value is lower. The description adds useful behavioral context beyond annotations: it does not connect automaticallyasi, it is a first-party directory, and it exposes setup-related information. No contradiction with 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?

The description is short and front-loaded with a [READ] marker and the core 'first-party Swarm MCP directory' statement, followed by guidance and an alternative. The ambiguous 'Use a focused endpoint...' sentence slightly detracts from clarity, but overall every sentence carries useful information with minimal waste.

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 zero-parameter, read-only discovery tool without an output schema, the description covers what the listing contains, that it won't auto-connect, and how to get broader results. It could be more explicit about the exact format of the returned data, but the content categories listed are sufficient for an agent to understand the tool's role.

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?

The tool takes zero parameters, so there is no schema burden to compensate for. The description appropriately explains what the returned directory contains, which is the most relevant semantic information for a no-input discovery tool.

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?

Description states a specific verb-like purpose: listing the first-party Swarm MCP directory, with concrete content categories (endpoints, categories, transport URLs, independent-session setup). It also differentiates from search_mcp_servers, so the agent can distinguish this resource-discovery tool from ecosystem-wide search.

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 explicitly points to search_mcp_servers as the alternative for broader ecosystem discovery, which provides an exclusion condition. However, the sentence 'Use a focused endpoint when its tools are not in this client's catalog' is slightly ambiguous about whether it means the user should invoke list_related_servers or some other endpoint, so it doesn't fully spell out when to prefer this tool.

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