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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds genuine context beyond them: the two resolution mechanisms for the binding and the explicit fallback contract when nothing is bound. It stops short of describing the success payload's fields, so it is not 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?

Two sentences, front-loaded with the primary behavior and followed by the edge case. Every clause carries information — binding source, return contract — with no restatement of the name or title.

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 return-value burden, and it covers the failure shape (active=false with guidance) but not the success payload's fields. For a zero-parameter read tool with annotations covering safety, this is close to complete, with only the success response under-specified.

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 are effectively zero parameters (the single '_unused' string is a placeholder with 100% coverage), so the baseline is 4. The description correctly implies the tool takes no user-supplied input and derives everything from session context, matching the schema.

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 ('Returns the project currently bound to this MCP session') and pins down the binding source (X-Project-Id header or API key's active_project_id). It separates itself from list_projects by scope, but never names a sibling such as set_active_project or whoami explicitly, so differentiation is inferential rather than stated.

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?

No when-to-use or when-not-to-use guidance is given, and no alternative is named. The closest thing is a behavioral note about the unbound case ('returns active=false with guidance'), which tells the agent what happens, not when to reach for this tool over set_active_project or get_linked_project.

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