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

Annotations only say readOnly/openWorld/non-idempotent; the description goes well beyond that, disclosing that the tool makes a live network call to a third-party endpoint, probes OAuth discovery on 401, distinguishes 402/403/401 semantics, and notes that a non-JSON-RPC 200 counts as unreachable. The `skipCredentialCheck` trade-off (one request vs. up to five, losing credential-obtainability reporting) is exactly the kind of behavioral detail annotations cannot carry.

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 the action, then a compact outcome glossary, then a one-line usage rule. Every sentence carries load — the outcome list substitutes for the absent output schema, and the base-rate sentence justifies the tool's existence.

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?

No output schema exists, and the description enumerates the full result vocabulary along with what each outcome means, so an agent knows exactly what it will get back. For a two-parameter, read-only diagnostic tool this leaves nothing material unspecified.

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 baseline is 3; the description earns a bump by pinning `name` to "the official MCP registry" and clarifying that credential-obtainability reporting is what `skipCredentialCheck` trades away, which gives the flag a decision-relevant meaning beyond the schema's speed note.

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: make one `initialize` call to the endpoint named in a registry listing and report what a credential-less client receives. The enumerated outcome vocabulary (`usable`, `needs_credential`, `charged`, `unreachable`, `local_only`, `not_listed`) makes the tool's scope unmistakable and distinct from the sibling `mcp_liveness_explain_outcomes`, which evidently only explains those outcomes.

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 an explicit trigger: "Call this before spending a call on a server you found in the catalogue," backed by a base-rate justification (two in five remote listings fail). No explicit when-not clause or named alternative, but the pre-flight positioning is clear enough to route correctly.

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