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

The annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so safety is covered. Beyond that, the description adds real operational context: the specific 409 NOT_CONNECTED error condition, the profile:read permission scope, the sign-in prompt for unconnected members, and a prompt-injection warning about member-written text. That is substantive behavior disclosure that the structured fields do not 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?

The description is front-loaded with the core purpose and then layers constraints, permission, and injection caveat in a logical order. The opening sentence duplicates the title almost verbatim, which is mild waste, but the rest of the text is dense with useful information and contains no filler.

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 output schema, the description carries the burden of explaining results, and it does so partially: endorsable skills and sections, each marked with existing endorsement state. It also covers the error and auth paths. The only gap is that the exact structure of the returned list and any pagination or ordering behavior are not described.

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?

There is a single parameter with 100% schema description coverage; the schema already explains that userId is a connection's member id from GET /me/connections. The description repeats the constraint that only connections qualify but adds no format or interpretation details beyond the schema. Baseline 3 is appropriate when the schema does the heavy lifting.

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 action and resource: the skills and profile sections on a connection's profile page that are endorsable, each flagged with whether the member already endorsed it. That is far more useful than the vague title alone. It does not explicitly name the neighboring tools (endorse_connection, list_my_endorsements, remove_endorsement) to distinguish itself from them, which keeps it one step short of a 5.

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 gives a clear negative condition: only a connection can be endorsed, and anyone else returns 409 NOT_CONNECTED. It also states the permission required (profile:read) and the sign-in behavior for members who have not yet connected. It stops short of naming alternatives such as endorse_connection for performing the endorsement or list_my_endorsements for viewing one's own endorsements.

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