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

Even though annotations already declare readOnlyHint=true and destructiveHint=false, the description adds valuable behavioral context: it reads the entire cookie jar, returns full values (including live session tokens), and can be filtered by URL. This goes well beyond the annotations and gives the agent important safety-relevant information.

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 concise, well-structured, and front-loaded with the primary purpose. Each sentence serves a purpose: the first states what it does, the second explains scope and sensitivity, and the third gives alternatives. No wasted words.

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?

The tool is simple (one optional parameter, read-only, output schema present), and the description covers all essential aspects: scope, filtering, sensitivity, and persistence alternatives. It is fully complete for an agent to select and invoke correctly.

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 schema already covers the url parameter's meaning at 100% (including the empty-string default). The description reinforces this by explaining the 'whole jar vs filtered by url' behavior, adding a practical nuance not fully captured in the schema. It doesn't duplicate everything, but it adds useful behavioral context around the parameter.

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 clearly states a specific action ('List browser cookies') with a defined resource and the fields returned (domain, path, secure flag). It also distinguishes itself from related tools like set_cookie, clear_cookies, and get_local_storage by specifying that it reads the whole cookie jar, not just the current page.

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 explicit usage context: it reads all cookies unless a url is passed, and notes that outputs are sensitive. It also names specific alternatives for persistence ('save_session' and 'use_profile'), providing clear when-to-use and when-to-avoid guidance.

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