get_thread

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

Beyond the readOnly/idempotent annotations, it discloses real behavior: the shared maxChars budget across messages, that short bodies stay whole while long ones are truncated and truncation is reported, and that email fields are untrusted data delimited by ⟦mail:ID⟧ markers with an explicit instruction not to follow embedded commands.

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?

Front-loaded purpose sentence, then the maxChars allocation rule, then the injection warning, then a compact Args block. No filler, though the Args list repeats parameter names already in the schema and available context.

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 an output schema present and annotations covering the safety profile, the description supplies exactly the missing pieces: budget/truncation semantics, parameter bounds, and the untrusted-content framing. An agent has everything needed to call this 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?

Schema coverage is 0%, so the description carries the full load and does: threadId is documented as coming from search_threads, and maxChars gets its unit ('total length of the bodies'), valid range 200–100,000, default 16,180, plus how the budget is allocated across messages — details absent from 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 ('Read a Gmail thread') and adds two distinguishing behavioral traits: messages are returned in order and quoted earlier replies ("> ", "On … wrote:") are stripped. That implicitly and clearly separates it from the sibling get_message, which reads a single message.

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: the threadId arg note '(returned by search_threads)' sketches the search-then-read workflow, but the description never states when to use this instead of search_threads or get_message, nor any exclusions. Adequate but leaves routing to inference.

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