diff --git a/packages/lp32/reader.js b/packages/lp32/reader.js
index d7b8f03720..e63d76dcf6 100644
--- a/packages/lp32/reader.js
+++ b/packages/lp32/reader.js
@@ -10,7 +10,7 @@ const { details: X, quote: q } = assert;
 
 /**
  * @param {Iterable<Uint8Array> | AsyncIterable<Uint8Array>} reader
- * @param {Object} [opts]
+ * @param {Object} opts
  * @param {string=} [opts.name]
  * @param {number} [opts.maxMessageLength] - defaults to 1MB
  * @param {boolean=} [opts.littleEndian]
diff --git a/packages/lp32/writer.js b/packages/lp32/writer.js
index d5156e9766..3cf8b52763 100644
--- a/packages/lp32/writer.js
+++ b/packages/lp32/writer.js
@@ -7,7 +7,7 @@ const { details: X, quote: q } = assert;
 
 /**
  * @param {import('@endo/stream').Writer<Uint8Array, undefined>} output
- * @param {Object} [opts]
+ * @param {Object} opts
  * @param {number} [opts.maxMessageLength] - defaults to 1MB
  * @param {string} [opts.name]
  * @param {boolean} [opts.littleEndian] - defaults to host byte order
diff --git a/packages/marshal/src/encodeToCapData.js b/packages/marshal/src/encodeToCapData.js
index 6638c09155..bb5b1ca54e 100644
--- a/packages/marshal/src/encodeToCapData.js
+++ b/packages/marshal/src/encodeToCapData.js
@@ -90,7 +90,7 @@ const dontEncodeErrorToCapData = err =>
   assert.fail(X`error object unexpected: ${err}`);
 
 /**
- * @param {EncodeToCapDataOptions} [encodeOptions]
+ * @param {EncodeToCapDataOptions} encodeOptions
  * @returns {(passable: Passable) => Encoding}
  */
 export const makeEncodeToCapData = ({
@@ -308,7 +308,7 @@ const dontDecodeErrorFromCapData = errorEncoding =>
  * API where these can reliably differ.
  * See https://github.com/Agoric/agoric-sdk/issues/4334
  *
- * @param {DecodeOptions} [decodeOptions]
+ * @param {DecodeOptions} decodeOptions
  * @returns {(encoded: Encoding) => Passable}
  */
 export const makeDecodeFromCapData = ({
diff --git a/packages/marshal/src/encodeToSmallcaps.js b/packages/marshal/src/encodeToSmallcaps.js
index 4dba916ec4..15f94d14eb 100644
--- a/packages/marshal/src/encodeToSmallcaps.js
+++ b/packages/marshal/src/encodeToSmallcaps.js
@@ -114,7 +114,7 @@ const dontEncodeErrorToSmallcaps = err =>
   assert.fail(X`error object unexpected: ${q(err)}`);
 
 /**
- * @param {EncodeToSmallcapsOptions} [encodeOptions]
+ * @param {EncodeToSmallcapsOptions} encodeOptions
  * @returns {(passable: Passable) => SmallcapsEncoding}
  */
 export const makeEncodeToSmallcaps = ({
@@ -343,7 +343,7 @@ const dontDecodeErrorFromSmallcaps = encoding =>
   assert.fail(X`error unexpected: ${q(encoding)}`);
 
 /**
- * @param {DecodeFromSmallcapsOptions=} decodeOptions
+ * @param {DecodeFromSmallcapsOptions} decodeOptions
  * @returns {(encoded: SmallcapsEncoding) => Passable}
  */
 export const makeDecodeFromSmallcaps = ({
diff --git a/packages/marshal/src/marshal.js b/packages/marshal/src/marshal.js
index b8ee9bf625..83def9e883 100644
--- a/packages/marshal/src/marshal.js
+++ b/packages/marshal/src/marshal.js
@@ -41,7 +41,7 @@ const defaultSlotToValFn = (x, _) => x;
  * @template Slot
  * @param {ConvertValToSlot<Slot>} [convertValToSlot]
  * @param {ConvertSlotToVal<Slot>} [convertSlotToVal]
- * @param {MakeMarshalOptions} [options]
+ * @param {MakeMarshalOptions} options
  */
 export const makeMarshal = (
   convertValToSlot = defaultValToSlotFn,
diff --git a/packages/netstring/reader.js b/packages/netstring/reader.js
index ce06b9101c..f8c644b269 100644
--- a/packages/netstring/reader.js
+++ b/packages/netstring/reader.js
@@ -8,7 +8,7 @@ const NINE = '9'.charCodeAt(0);
 
 /**
  * @param {Iterable<Uint8Array> | AsyncIterable<Uint8Array>} input
- * @param {Object} [opts]
+ * @param {Object} opts
  * @param {string} [opts.name]
  * @param {number} [opts.maxMessageLength]
  */
diff --git a/packages/netstring/writer.js b/packages/netstring/writer.js
index f7f67ebc46..d85fe29588 100644
--- a/packages/netstring/writer.js
+++ b/packages/netstring/writer.js
@@ -20,7 +20,7 @@ const getLengthPrefixCharCodes = length =>
  * to avoid pre-concatenating them.
  *
  * @param {import('@endo/stream').Writer<Uint8Array, undefined>} output
- * @param {object} [opts]
+ * @param {object} opts
  * @param {boolean} [opts.chunked]
  * @returns {import('@endo/stream').Writer<Uint8Array | Uint8Array[], undefined>}
  */