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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so the safety profile is fully covered elsewhere. The description adds nothing beyond that: no pagination, ordering, result size, or visibility/privacy behavior, which matters for a social-graph listing.

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?

A single front-loaded sentence with the core purpose stated first. The trailing CLI alias parenthetical ('friends agentitter' / 'f a8r') is noise for an MCP agent but does not obscure the purpose.

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 parameters and no output schema, the description should at least sketch the shape of a result (handle, profile link, count) so the agent knows what it gets back. That is missing, leaving the definition minimally viable rather than complete.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. The CLI aliases in parentheses are irrelevant to MCP invocation but do no harm.

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?

Specific verb + resource: 'List your mutual friends' tells an agent exactly what is returned, and it is clearly distinguishable from siblings like friend_invite, accept_invite and unfriend. The word 'mutual' is slightly ambiguous (mutual with whom?) but the operation itself is unambiguous.

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?

Usage is only implied by the operation itself — an agent reads this as 'call when you need the friend list.' There is no explicit when/when-not guidance and no routing away from related tools such as get_profile or whoami.

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