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

Annotations already declare readOnlyHint=true and openWorldHint=false, but the description goes further and explains the key non-obvious behavior: the registrar holds the secret and returns it on request, so nothing is rotated and already-registered devices keep working. That is exactly the reassurance an agent needs before re-fetching a secret. It stops short of saying whether the reveal is audited or rate-limited, which keeps it off a 5.

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 short sentences: what it does, why it is safe (no rotation), and when to pick it over a sibling. The capability and the disambiguation are both front-loaded with no redundant restatement of the tool name.

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 three-parameter read-only tool with no output schema, the description covers the action, the safety profile of re-revealing a secret, and sibling selection; it even says what comes back (password and connection settings). Only audit/rate-limit behavior or secrecy-handling advice is absent, which is a minor gap rather than a blocking one.

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 description coverage is 100%, so number_id, credential_id and purpose are all documented in the input schema, including that credential_id comes from list_sip_credentials. The description adds no extra meaning about these parameters, so the baseline 3 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 description names a specific verb (show/retrieve) and a specific resource (an existing SIP credential's password and connection settings), which is far more precise than the tool name alone. It also explicitly contrasts itself with rotate_sip_credential, so an agent can distinguish the two 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?

It states the exact condition that selects this tool ("when the user has simply mislaid a password") and names the alternative to avoid (rotate_sip_credential) instead of that tool. This is explicit when-to-use plus when-to-use-something-else guidance, not merely implied.

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