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

With no annotations present, the description carries the full burden and does so richly: the old token is REVOKED immediately, default lifetime is 1 year, the new token is auto-applied inside the MCP session but must be saved for raw HTTP, and the X-Token-Expires-At header plus 30-day warning are documented. It also states the precondition (a valid, non-expired token).

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 core exchange action and mostly dense, but the revocation fact is stated twice ('REVOKES the old token immediately' and again 'The old token is revoked'), which is redundant.

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?

With no annotations and no output schema, the description covers return values (token + token_expires_at), preconditions, session behavior, and error path. An agent has everything needed to call it correctly.

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 0%, so the description must compensate, and it does: it gives expires_in_days its default (1 year) and valid range (1-1825), which the bare integer schema with only min/max does not convey in prose.

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+resource: 'Exchange the CURRENT bearer token for a new one'. It distinguishes itself from the nearest sibling by naming 'login' as the fallback path for expired tokens, so an agent can tell it apart without opening either 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?

Explicit when-to-use ('before it expires'), when-not ('An already expired token cannot be refreshed'), and the alternative ('log in again (login) or create a token in the cabinet'). Nothing about routing is left to inference.

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