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

Annotations already declare readOnlyHint=false, openWorldHint=true, idempotentHint=false and destructiveHint=false, so the safety profile is covered. The description adds value beyond that by stating the required permission scope ('user:write') and the expected input provenance (.pub file). It does not disclose what happens on a duplicate key or duplicate name, which is the remaining behavioral gap.

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?

Two short sentences with no filler; the core action is front-loaded and the permission requirement follows immediately. Every sentence earns its place.

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 small two-parameter mutation with full schema coverage, no output schema, and annotations carrying the safety hints, the description covers action, input format and required permission. It stops short of noting duplicate-key/name behavior, which an agent handling idempotency=false would benefit from knowing.

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 both parameters (name, public_key) are already documented with examples and length bounds, making 3 the baseline. The description's 'a line from a .pub file' adds only marginal format context beyond the schema's own 'ssh-ed25519 AAAA… you@laptop' example.

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 ('Adds an SSH public key ... to the account') and even clarifies the input format ('a line from a .pub file'), so the operation is unambiguous. It never names or contrasts with its natural counterpart list_ssh_keys, so sibling differentiation is only implicit via the verb.

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?

The description supplies a real prerequisite ('Needs user:write'), which tells the agent what authorization is required before calling. However, it gives no when-to-use framing, no exclusions, and no routing toward alternatives such as list_ssh_keys for verification, leaving usage only implied.

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