session_read_page

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

Annotations already establish read-only, idempotent, open-world behavior, so the description adds value by disclosing the exact returned fields, the 50,000-character cap, the truncated flag semantics, and that text is rendered innerText from the authenticated session. This goes beyond the structured annotations without contradicting them.

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?

Three concise, purposeful sentences: what it does, what it returns with key limits, and when to use it vs. a sibling. Every sentence earns its place and the most important behavior is front-loaded.

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 one-optional-parameter read tool with no output schema, the description fully specifies the return shape, the truncation behavior, and the sibling distinction. The agent has everything needed to invoke it correctly and understand the result.

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 documents tabId with its integer type and default behavior ('uses the active tab when omitted'), so schema description coverage is 100%. The description does not add parameter-level detail, but none is needed given the schema's completeness.

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 uses a specific verb and resource ('Read a page's visible text, as rendered in the user's authenticated session') and immediately contrasts with session_snapshot by scoping this tool to reading/summarizing rather than interacting. This clearly distinguishes it from its sibling tools.

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 explicitly states when to prefer this tool over session_snapshot ('when the goal is to read or summarise') and when to prefer the alternative ('when the goal is to interact'). This gives the agent direct routing guidance.

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