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

With no annotations provided, the description carries full behavioral disclosure burden. It discloses the persistent nature (auto-prepended to system prompt on every chat), the 10240-byte cap with 413 over-cap behavior, and formatting expectations. Does not mention whether appends can be deleted or overwritten beyond the sibling replace tool, but covers the key side effects affecting agent decisions.

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 tight sentences with zero waste. Front-loaded purpose, then usage rules, then constraints. Every clause earns its place—trigger phrases, anti-pattern warning, memory behavior, cap, formatting guidance.

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 1-parameter tool with 100% schema coverage and no output schema, the description is highly complete. It covers when to use, what to store, storage behavior, and failure mode. Minor gap: doesn't describe what happens on success (return value), but for a side-effect append operation this is a low-value omission given no output schema is 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?

Schema description coverage is 100%, so the single 'block' parameter is fully documented in the schema. The description adds the value-laden guidance that markdown is encouraged and entries should be terse and factual, which is useful but the schema already defines what the parameter is. Baseline 3 is appropriate.

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?

Clear specific verb+resource: 'Append a block to the calling user's persistent agent memory.' Distinguishes from sibling agent_memory_replace by specifying append semantics, and from the large pool of device/test tools by its explicit memory scope.

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?

Exceptionally explicit: names exact trigger phrases ('remember X', 'save this', 'note for next time'), states an explicit exclusion ('DO NOT auto-update on every interaction'), and gives content guidance (terse, factual, markdown, not verbose). This is textbook-level usage guidance.

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