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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the description adds value by disclosing the return shape ({ id, name, role, permissions }) and the meaning of an empty array (key valid but no application bound). What it does not cover — pagination, ordering, error behavior on invalid keys — is minor for a zero-arg read, so a 4 rather than 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?

Four short sentences ordered by utility: what it returns, when to call it, invocation cost, then the response contract. Every sentence carries a distinct fact and the routing guidance is front-loaded.

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-param, read-only tool with no output schema, the description supplies the missing pieces an agent needs: the response fields, the empty-array interpretation, and its bootstrap role for personal API keys. Nothing required to call or interpret it is absent.

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?

With zero parameters the baseline is 4, and the description reinforces this by stating 'takes no arguments', removing any doubt about how to invoke it. No additional parameter meaning is needed because none exist.

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 ('List the applications this API key can access') and immediately scopes it to the caller's role and permissions. It is unmistakable against siblings like list_contacts or get_application_context because it defines the access-discovery role rather than a domain listing.

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?

Explicitly says when to use it: 'Start here when using a personal API key (usr_...)'. It also names the dependency that selects it — every other tool needs an explicit applicationId, which only this tool supplies — giving the agent both the trigger and the downstream consequence.

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